diff --git a/.gitignore b/.gitignore
index 1c6eb68..fe7f0cf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,4 +10,7 @@ a.out
 roms/
 third_party/fmt
 bios.bin
-*.sav
\ No newline at end of file
+*.sav
+*.swp
+./.tags
+
diff --git a/Makefile b/Makefile
index 9c14c29..af61464 100644
--- a/Makefile
+++ b/Makefile
@@ -6,10 +6,10 @@ SOURCE = src
 INCLUDE = include
 BACKUPDIR = $(INCLUDE)/backup
 OBJ = \
+	config.o \
 	APU.o \
 	Arm7.o \
 	arm_isa.o \
-	config.o \
 	Discovery.o \
 	Flash.o \
 	Gamepad.o \
@@ -33,6 +33,12 @@ ifdef opt
 CXXFLAGS += -Ofast
 endif
 
+# Use verbose output
+# run `make verbose=1`
+ifdef verbose
+CXXFLAGS += -Wall -pedantic
+endif
+
 all: discovery
 discovery: $(LIST) main.cpp
 	$(CXX) $(CXXFLAGS) -o discovery $(SOURCE)/main.cpp $(LIST) $(LIBS)
diff --git a/README.md b/README.md
index bba56dd..111ba06 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,65 @@ Discovery will attempt to load a BIOS in the same directory as the executable ca
 
 `./discovery path/to/rom -b path/to/bios`
 
+### Flags
+
+| Flag | | Type | Description|
+|----|----|----|----|
+`-i` | `--input` | `string` | Specify the input ROM
+`-b` | `--bios` | `string` | Specify the BIOS Discovery will use
+`-c` | `--config` | `string` | Specify the config file Discovery will use
+`-h` | `--help` | `boolean` | Print Discovery help
+
+## Configuration
+
+By default Discovery will load and read settings from a file named `discovery.config`. Alternatively, you can load from a different config file
+using: 
+
+`./discovery -c my_alt_config.file`
+
+The syntax for a config file is very simple. Key-value pairs are set like so:
+
+```
+# this is a comment
+set_key = values_like_this
+```
+
+Below is a table describing the keys Discovery will recognize.
+
+### Configuration options
+
+|Key | Description|
+|----|----|
+`gba_a         `  | Map the A button to the specified key
+`gba_b         `  | Map the B button to the specified key
+`gba_sel       `  | Map the Select button to the specified key
+`gba_start     `  | Map the Start button to the specified key
+`gba_dpad_right`  | Map right on the dpad to the specified key
+`gba_dpad_left `  | Map left on the dpad to the specified key
+`gba_dpad_up   `  | Map up on the dpad to the specified key
+`gba_dpad_down `  | Map down on the dpad the specified key
+`gba_r         `  | Map the R button to the specified key
+`gba_l         `  | Map the L button to the specified key
+
+#### Example
+
+This example config file will map controls to WASD keys, using the k, l, o, and p 
+keys for the A, B, L and R buttons, respectively:
+
+```
+# map buttons to WASD controls
+gba_dpad_up = w 
+gba_dpad_down = s
+gba_dpad_left = a
+gba_dpad_right = d
+gba_a = k
+gba_b = l
+gba_r = o
+gba_l = p
+gba_start = cr
+gba_sel = bs
+```
+
 ## Building on Linux based systems
 Discovery has the following dependencies:
 - make
diff --git a/discovery.config b/discovery.config
new file mode 100644
index 0000000..753ecc0
--- /dev/null
+++ b/discovery.config
@@ -0,0 +1,12 @@
+# map keys
+gba_dpad_up = up
+gba_dpad_down = down
+gba_dpad_left = left
+gba_dpad_right = right
+gba_a = x
+gba_b = z
+gba_r = s
+gba_l = a
+gba_start = cr
+gba_sel = bs
+
diff --git a/docs/assets/9600204_orig.gif b/docs/assets/9600204_orig.gif
new file mode 100644
index 0000000..45b792c
Binary files /dev/null and b/docs/assets/9600204_orig.gif differ
diff --git a/docs/assets/Minimoog_1979_left_2017_right.jpg b/docs/assets/Minimoog_1979_left_2017_right.jpg
new file mode 100644
index 0000000..014cdcc
Binary files /dev/null and b/docs/assets/Minimoog_1979_left_2017_right.jpg differ
diff --git a/docs/css/styles.css b/docs/css/styles.css
index 1a73eac..0714666 100644
--- a/docs/css/styles.css
+++ b/docs/css/styles.css
@@ -81,3 +81,24 @@ hr {
 .bl {
   margin-bottom: 16px;
 }
+
+.figure {
+  display: flex;
+  flex-direction: column;
+  margin-top: 2rem;
+  margin-bottom: 2rem;
+}
+
+.figure-text {
+  margin-left: auto;
+  margin-right: auto;
+  max-width: 66.66666%;
+  margin-top: .5rem;
+}
+
+.figure-image {
+  margin-left: auto;
+  margin-right: auto;
+  max-width: 81.33333%;
+  max-height: 81.33333%;
+}
diff --git a/docs/docs.html b/docs/docs.html
index b02d837..762e34b 100644
--- a/docs/docs.html
+++ b/docs/docs.html
@@ -74,34 +74,49 @@ <h5 class="toc-header"> Table of contents </h5>
               <a href="#sound-resources" class="section"><li>Sound resources</li></a>
               <ul>
                 <li>Register details:
-                <a href=">http://www.belogic.com/gba/registers.shtml">http://www.belogic.com/gba/registers.shtml></a></li>
+                <a href="http://www.belogic.com/gba/registers.shtml">http://www.belogic.com/gba/registers.shtml></a></li>
 
                 <li>SDL sound spec:
-                <a href=">https://wiki.libsdl.org/SDL_AudioSpec">https://wiki.libsdl.org/SDL_AudioSpec></a></li>
+                <a href="https://wiki.libsdl.org/SDL_AudioSpec">https://wiki.libsdl.org/SDL_AudioSpec></a></li>
 
                 <li>Sound generator:
-                <a href=">https://stackoverflow.com/questions/10110905/simple-sound-wave-generator-with-sdl-in-c">https://stackoverflow.com/questions/10110905/simple-sound-wave-generator-with-sdl-in-c></a></li>
+                <a href="https://stackoverflow.com/questions/10110905/simple-sound-wave-generator-with-sdl-in-c">https://stackoverflow.com/questions/10110905/simple-sound-wave-generator-with-sdl-in-c></a></li>
 
                 <li>Sound / opening the audio device:
-                <a href=">https://web.archive.org/web/20130724194546/http://www.libsdl.org:80/intro.en/usingsound.html">https://web.archive.org/web/20130724194546/http://www.libsdl.org:80/intro.en/usingsound.html></a></li>
+                <a href="https://web.archive.org/web/20130724194546/http://www.libsdl.org:80/intro.en/usingsound.html">https://web.archive.org/web/20130724194546/http://www.libsdl.org:80/intro.en/usingsound.html></a></li>
 
                 <li>Tone generator reference:
-                <a href=">https://github.com/psycotica0/tone-generator/blob/master/generator.c">https://github.com/psycotica0/tone-generator/blob/master/generator.c></a></li>
+                <a href="https://github.com/psycotica0/tone-generator/blob/master/generator.c">https://github.com/psycotica0/tone-generator/blob/master/generator.c></a></li>
 
                 <li>GBA audio in depth:
-                <a href=">https://www.coranac.com/tonc/text/sndsqr.htm#sec-intro">https://www.coranac.com/tonc/text/sndsqr.htm#sec-intro></a></li>
+                <a href="https://www.coranac.com/tonc/text/sndsqr.htm#sec-intro">https://www.coranac.com/tonc/text/sndsqr.htm#sec-intro></a></li>
 
                 <li>SDL sine wave generator:
-                <a href=">https://gist.github.com/MasterQ32/46ffd78a6cf261c73a1fddb93a478ebe">https://gist.github.com/MasterQ32/46ffd78a6cf261c73a1fddb93a478ebe></a></li>
+                <a href="https://gist.github.com/MasterQ32/46ffd78a6cf261c73a1fddb93a478ebe">https://gist.github.com/MasterQ32/46ffd78a6cf261c73a1fddb93a478ebe></a></li>
 
                 <li>Spongebob square wave:
-                <a href=">https://davidgow.net/handmadepenguin/ch8.html">https://davidgow.net/handmadepenguin/ch8.html></a></li>
+                <a href="https://davidgow.net/handmadepenguin/ch8.html">https://davidgow.net/handmadepenguin/ch8.html></a></li>
 
                 <li>More details :
-                <a href=">https://www.problemkaputt.de/gbatek.htm#gbasoundchannel1tonesweep">https://www.problemkaputt.de/gbatek.htm#gbasoundchannel1tonesweep></a></li>
+                <a href="https://www.problemkaputt.de/gbatek.htm#gbasoundchannel1tonesweep">https://www.problemkaputt.de/gbatek.htm#gbasoundchannel1tonesweep></a></li>
 
                 <li>Sound timing:
-                <a href=">http://ianfinlayson.net/class/cpsc305/notes/19-sound">http://ianfinlayson.net/class/cpsc305/notes/19-sound></a></li>
+                <a href="http://ianfinlayson.net/class/cpsc305/notes/19-sound">http://ianfinlayson.net/class/cpsc305/notes/19-sound></a></li>
+
+                <li>
+                  Fourier transform within window function:
+                  <a href="https://stackoverflow.com/questions/43479528/how-can-i-perform-a-realtime-fft-on-sdl2-audio-stream-data">https://stackoverflow.com/questions/43479528/how-can-i-perform-a-realtime-fft-on-sdl2-audio-stream-data</a>
+                </li>
+                <li>SDL Audio callback locking:
+                <a href="https://wiki.libsdl.org/SDL_LockAudioDevice">https://wiki.libsdl.org/SDL_LockAudioDevice</a>i
+                </li>
+                <li>
+                  Nyquist-Shannon sampling theorem for brudging between continuous-time 
+                  signals and discrete-time signals
+                  <a href="https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem">
+                    https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
+                  </a>
+                </li>
               </ul>
             </div>
 
@@ -111,13 +126,27 @@ <h5 class="toc-header"> Table of contents </h5>
             <div class="bl">
               <a href="#fourier" class="section"><li>Fourier transform</li></a>
               
-              <div class="equation" id="eq1.0"></div>
               <script>
+                // fourier
                 el = document.getElementById("eq1.0")
                 eq = `
-                  \\hat{f}(\\xi) = \\int_{-\\infty}^{\\infty}f(x)e^{-2 \\pi i x \\xi}\\, dx
+                  \\hat{f}(\\xi) = \\int_{t_0}^{t_1}f(t)e^{-2 \\pi i t \\xi}\\, dt
                 `
                 this.latex.render(eq, el)
+
+                // xi
+                el = [...document.getElementsByClassName("xi")]
+                eq = `
+                  \\xi
+                `
+                this.latex.render(eq, el, false)
+
+                // t
+                el = [...document.getElementsByClassName("t")]
+                eq = `
+                  t
+                `
+                this.latex.render(eq, el, false)
               </script>
               Just trying out <span id="latex0"></span> in HTML
               <script>
diff --git a/docs/js/render.js b/docs/js/render.js
index f95ddd0..34e7cad 100644
--- a/docs/js/render.js
+++ b/docs/js/render.js
@@ -10,14 +10,15 @@ const renderEl = (str, el, displayMode, handleErr) => {
 const render = (str, el, displayMode=true, handleErr=false) => {
   if(window.katex) {
     if(el instanceof Array) {
-      if(str instanceof String) {
-        el.forEach((e, i) => {
-          renderEl(str[i], e, displayMode, handleErr)
-        })
-      } else {
+      if(typeof str === "string") {
         el.forEach((e) => {
+          console.log(e)
           renderEl(str, e, displayMode, handleErr)
         })
+      } else {
+        el.forEach((e, i) => {
+          renderEl(str[i], e, displayMode, handleErr)
+        })
       }
     } else if(str && el) {
       renderEl(str, el, displayMode, handleErr)
diff --git a/docs/scripts/fourier.py b/docs/scripts/fourier.py
new file mode 100644
index 0000000..edd3ead
--- /dev/null
+++ b/docs/scripts/fourier.py
@@ -0,0 +1,4 @@
+from matplotlib import pyplot as plt
+arr = 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,0,1,6,22,0,1,8,29,12,14,10,4,3,6,3,10,2,29,14,7,1,1,3,4,7,2,9,35,51,17,12,3,14,1,12,13,12,5,13,9,0,16,16,14,12,4,13,9,43,13,8,2,10,2,11,2,3,2,6,0,9,6,3,1,0,0,0,3,7,7,9,18,10,4,2,7,1,1,0,5,3,19,23,13,12,0,8,2,2,3,12,19,6,15,4,4,2,8,5,0,0,4,1,2,10,0,12,5,5,2,4,17,16,6,7,11,1,6,10,0,1,14,15,1,61,43,23,24,6,8,3,17,3,26,15,39,28,22,9,5,9,0,2,5,4,1,6,10,6,0,4,0,2,2,3,1,2,3,1,3,1,1,0,4,5,7,2,6,32,20,3,6,2,3,0,11,9,12,1,1,7,10,1,10,1,6,5,10,1,15,8,10,0,3,1,5,2,0,1,31,48,16,6,5,7,0,9,5,20,6,7,4,3,4,14,5,6,1,15,12,34,13,40,16,8,6,10,1,3,4,7,0,3,4,6,4,1,0,0,0,3,2,17,32,13,2,6,6,1,3,4,6,6,22,27,10,8,2,3,0,5,4,18,27,5,18,20,6,4,12,3,1,3,7,0,0,13,1,11,4,2,0,2,7,11,20,40,23,4,10,11,4,4,13,5,10,51,46,14,16,2,3,4,15,7,32,33,29,14,37,1,8,15,0,2,4,7,0,0,3,5,5,0,0,0,0,4,4,13,27,12,1,6,5,1,2,7,3,6,26,34,13,9,1,3,2,6,1,20,25,10,12,22,6,4,12,2,1,3,7,0,0,7,3,8,1,1,0,1,6,7,14,31,17,2,8,8,3,2,11,2,8,40,43,15,13,3,3,3,11,2,27,28,21,10,29,3,5,14,1,2,3,6,0,1,3,3,7,0,1,1,0,5,6,11,26,13,1,6,6,2,1,10,0,7,33,41,16,11,4,3,3,9,0,23,25,17,8,25,4,4,13,1,1,3,5,0,4,1,3,7,0,1,2,0,6,6,6,19,11,0,6,5,2,0,12,3,6,33,45,20,11,7,2,5,9,3,23,21,18,2,24,5,3,13,1,0,0,1,1,0,0,1,1,2,1,0,1,0,1,0,9,12,1,0,2,1,1,3,1,9,5,7,2,4,0,2,1,0,2,7,5,7,0,21,11,0,3,2,0,0,1,0,0,3,1,0,1,0,0,0,1,2,1,3,6,0,1,1,0,1,1,3,6,5,3,3,2,2,0,2,1,1,4,4,2,0,17,9,0,2,2,0,0,1,0,0,1,0,1,1,0,0,0,0,2,1,6,9,0,0,1,0,1,2,1,8,5,2,1,4,2,1,1,0,1,5,3,5,2,19,9,1,2,2,0,0,1,0,0,0,0,1,0,0,0,1,0,3,2,6,11,0,0,1,0,1,2,0,9,5,1,0,5,3,2,1,0,0,5,2,5,5,20,7,2,2,2,0,0,1,0,0,0,0,1,1,0,0,0,0,2,1,7,10,1,0,1,0,1,2,1,8,5,2,1,4,1,2,1,0,0,6,3,5,2,20,9,1,2,2,0,0,1,1,0,0,0,1,0,0,0,1,0,3,1,7,11,1,0,1,0,1,3,0,9,5,0,0,5,2,2,1,0,0,6,2,6,4,20,8,1,2,2,0,0,1,1,0,0,0,1,0,0,0,1,0,2,1,7,11,1,0,1,0,1,3,0,9,5,1,0,5,2,2,1,0,0,6,3,6,3,21,9,1,2,2,0,0,1,1,0,0,0,1,0,0,0,1,0,2,1,8,12,1,0,1,0,1,3,0,9,5,2,0,5,1,3,1,0,0,7,3,7,3,21,9,1,2,2,0,0,1,0,0,4,7,3,0,0,1,0,0,0,0,1,3,7,3,0,1,0,0,0,0,0,3,7,6,2,1,1,1,0,1,0,3,3,6,1,1,1,1,1,2,1,2,0,2,0,5,1,1,0,3,1,4,7,9,10,2,0,0,2,0,2,3,12,5,12,16,8,6,7,2,1,2,8,3,3,11,30,3,0,5,0,0,1,1,2,0,0,0,2,0,0,0,1,0,2,2,7,11,3,0,1,0,0,2,0,8,4,0,0,1,1,2,0,0,0,5,1,7,3,20,6,2,3,1,0,0,0,2,0,3,6,0,2,0,1,1,0,3,1,11,25,12,4,4,4,3,5,1,11,7,7,8,2,1,1,1,0,2,8,9,15,4,21,13,4,3,4,1,0,1,1,0,0,0,1,1,0,0,1,0,1,0,6,11,3,0,1,0,1,2,0,7,4,2,4,0,0,1,0,0,0,4,3,8,1,17,7,2,3,2,0,0,1,2,0,1,3,0,2,0,0,1,0,2,0,8,17,7,2,3,2,2,3,1,8,5,6,8,0,1,1,0,0,1,6,6,12,2,18,10,3,3,3,0,0,1,1,0,0,1,1,1,0,0,0,0,1,0,7,13,4,1,2,1,2,2,1,6,4,5,8,1,1,0,0,0,1,4,5,10,1,15,8,3,2,3,0,0,1,1,0,0,0,0,2,0,0,0,0,1,1,6,11,3,0,2,2,2,2,2,4,3,8,11,3,3,0,0,1,1,3,5,10,2,12,8,3,2,3,0,1,4,2,6,3,33,12,6,6,2,5,9,6,13,0,47,60,8,12,1,10,1,22,25,40,1,16,34,32,0,29,7,16,14,36,8,37,41,62,1,10,1,2,9,4,3,0,1,3,25,2,26,19,12,2,10,15,27,39,28,11,3,12,20,1,13,18,11,7,108,25,2,36,8,9,2,30,34,33,23,57,25,51,33,24,5,2,1,1,0,0,0,8,0,8,7,4,1,3,1,7,17,14,2,0,4,6,1,7,4,11,5,32,1,8,9,6,1,0,9,17,9,8,14,24,19,11,10,0,2,4,2,7,1,27,12,5,3,1,3,4,6,1,6,29,40,11,11,1,11,1,12,16,13,6,0,6,7,10,17,11,12,7,14,0,31,18,9,6,8,2,5,1,1,0,0,0,0,3,0,3,3,1,1,1,2,1,11,10,0,0,1,2,1,5,0,11,4,10,6,9,1,5,0,0,3,12,2,4,1,23,10,5,5,0,1,2,0,3,0,12,5,2,1,0,1,1,3,2,4,10,15,6,5,0,5,1,3,6,0,5,4,3,2,7,5,7,5,2,2,2,14,3,8,4,3,2,3,0,1,0,1,0,4,2,0,0,0,0,0,1,4,3,0,1,3,2,0,2,1,1,0,7,4,6,9,8,6,1,4,1,0,4,3,4,4,18,3,1,2,2,1,0,0,1,0,1,4,0,4,2,2,1,2,8,7,1,3,4,0,1,4,1,2,5,11,3,24,17,12,11,4,4,1,6,5,9,2,18,23,4,4,0,2,0,1,3,2,1,5,8,4,0,2,0,1,1,1,1,0,0,5,3,0,1,0,1,3,3,0,4,18,12,2,3,2,2,0,5,3,7,2,3,3,5,0,5,0,4,2,6,0,7,3,7,0,2,0,4,0,2,5,18,26,8,2,2,1,0,5,4,16,6,4,8,6,2,10,0,3,2,11,3,16,12,35,8,4,5,4,0,2,2,4,0,1,2,4,2,0,0,1,0,0,0,11,20,7,1,3,2,1,3,1,8,5,8,11,3,2,2,1,0,2,5,8,15,0,20,12,4,4,6,1,0,1,5,0,2,9,0,6,2,0,1,1,1,5,15,32,17,4,7,7,4,5,6,9,8,25,24,4,7,0,0,2,7,8,19,23,14,19,23,3,5,9,0,1,2,4,0,0,1,3,2,0,0,0,0,0,1,9,18,7,1,3,3,1,2,3,5,5,12,16,5,4,0,1,1,3,3,10,15,3,15,13,4,3,6,0,0,2,4,0,0,4,1,4,1,0,0,0,1,3,11,24,11,2,5,5,2,3,5,6,6,20,23,6,6,0,0,2,5,5,15,19,10,15,18,3,4,8,0,1,2,3,0,0,2,2,4,0,0,0,0,1,2,9,19,8,1,4,3,2,2,5,4,5,17,22,7,5,1,1,2,4,3,13,16,7,13,16,4,3,7,0,0,2,3,0,2,]
+plt.plot(arr)
+plt.show()
diff --git a/include/APU.h b/include/APU.h
index cb21a12..b5850f1 100644
--- a/include/APU.h
+++ b/include/APU.h
@@ -35,7 +35,8 @@ class APU
 	
 private:
     AudioStat *stat;
-	int driver_id; // SDL audio device driver
+  	int driver_id; // SDL audio device driver
     u64 ticks;
     u64 ticks_until_next_buffer = 0;
-};
\ No newline at end of file
+};
+
diff --git a/include/APU.inl b/include/APU.inl
new file mode 100644
index 0000000..619088d
--- /dev/null
+++ b/include/APU.inl
@@ -0,0 +1,74 @@
+// apu inline methods
+
+// inline s16 APU::getChannelStream(int channel_index, int buffer_index) {
+// 	return this->channel[channel_index].stream[buffer_index];
+// }
+
+// inline void APU::setChannelStream(int channel_index, u16 data_buffer_len, s16 *stream_data) {
+// 	this->buffer_len = data_buffer_len;
+// 	std::memcpy(this->channel[channel_index].stream, stream_data, data_buffer_len * sizeof(stream_data));
+// }
+
+inline int APU::getAmplitude() {
+	return this->AMPLITUDE;
+}
+
+inline void APU::setAmplitude(int val) {
+	this->AMPLITUDE = val;
+}
+
+inline int APU::getSampleRate() {
+	return this->SAMPLE_RATE;
+}
+
+inline void APU::setSampleRate(int val) {
+	this->SAMPLE_RATE = val;
+}
+
+inline int APU::getBufferSize() {
+	return this->BUFFER_SIZE;
+}
+
+inline int APU::getSampleCount() {
+	return this->NUM_SAMPLES;
+}
+
+inline u16 APU::getBufferLength() {
+	return this->BUFFER_LEN;
+}
+
+inline void APU::setBufferLength(u16 val) {
+	this->BUFFER_LEN = val;
+}
+
+inline s8 APU::getDriverID() { 
+	return this->driver_id; 
+}
+
+inline void APU::setDriverID(s8 val) {
+	this->driver_id = val;
+}
+
+// inline u32 APU::getInternalBufferSize(u8 channel) {
+// 	return this->channel[channel].stream.size();
+// }
+
+// inline void APU::popInternalBuffer(u8 channel) {
+// 	this->channel[channel].stream.pop_back();
+// }
+
+inline double APU::getSamplesPerFrame() {
+	return this->SAMPLE_RATE / config::framerate * 2;
+}
+
+inline double APU::getBytesPerFrame() {
+	return this->getSamplesPerFrame() * this->NUM_SAMPLES;
+}
+
+inline double APU::getAudioBufferSize() {
+	return this->getBytesPerFrame() * 10;
+}
+
+// inline CircularBuffer<s16> *APU::getAudioBufferRef() {
+// 	return this->audio_buffer;
+// }
diff --git a/include/Discovery.h b/include/Discovery.h
index 47b3470..81f4ca4 100644
--- a/include/Discovery.h
+++ b/include/Discovery.h
@@ -40,4 +40,5 @@ class Discovery
     void parseArgs();
     void printArgHelp();
     void shutdown();
-};
\ No newline at end of file
+};
+
diff --git a/include/Gamepad.h b/include/Gamepad.h
index be1bdc8..5c8e49f 100644
--- a/include/Gamepad.h
+++ b/include/Gamepad.h
@@ -12,6 +12,7 @@
 
 #include <SDL2/SDL.h>
 #include "common.h"
+#include "log.h"
 
 class Gamepad
 {
@@ -78,6 +79,6 @@ class Gamepad
     void writeCnt(u16 val) { keycnt.raw = val; }
     void poll();
 
-private:
+    private:
     void checkInterrupt();
-};
\ No newline at end of file
+};
diff --git a/include/Memory.h b/include/Memory.h
index 484c655..6c983e5 100644
--- a/include/Memory.h
+++ b/include/Memory.h
@@ -139,4 +139,4 @@ class Memory
         APU *apu;
         AudioStat *audio_stat;
         Backup *backup;
-};
\ No newline at end of file
+};
diff --git a/include/PPU.h b/include/PPU.h
index b6f7e7f..795428b 100644
--- a/include/PPU.h
+++ b/include/PPU.h
@@ -141,4 +141,4 @@ class PPU
 
     u32 color_lut[0x8000];
     inline u32 u16ToU32Color(u16);
-};
\ No newline at end of file
+};
diff --git a/include/Scheduler.h b/include/Scheduler.h
index 3a4fa25..b040011 100644
--- a/include/Scheduler.h
+++ b/include/Scheduler.h
@@ -10,6 +10,12 @@ class Scheduler
     Scheduler() { cycles = 0; }
 
     u64 cycles;
+
+    /**
+     * @param until n cycles until the callback function is called
+     * @param handler callback function
+     * @param id event id
+     */
     void add(int, std::function<void(void)>, int id = -1);
     void advance(int);
     void remove(int);
diff --git a/include/audio_stat.h b/include/audio_stat.h
index 38ea57c..a9383c2 100644
--- a/include/audio_stat.h
+++ b/include/audio_stat.h
@@ -162,7 +162,7 @@ struct AudioStat
         sndcnt1_h.raw = 0;
         sndcnt1_x.raw = 0;
         sndcnt2_l.raw = 0;
-        sndcnt2_h.raw = 0;
+        sndcnt2_h.raw = 0; 
         sndcnt3_l.raw = 0;
         sndcnt3_h.raw = 0;
         sndcnt3_x.raw = 0;
@@ -170,4 +170,5 @@ struct AudioStat
         for (int i = 0; i < 32; ++i)
             wave_ram[i] = 0;
     }
-};
\ No newline at end of file
+};
+
diff --git a/include/common.h b/include/common.h
index a642ec5..21bb882 100644
--- a/include/common.h
+++ b/include/common.h
@@ -11,8 +11,8 @@
 
 #include <cstdint>
 #include <cstring>
-
-#include "log.h"
+#include <map>
+#include <SDL2/SDL.h>
 
 using u8  = std::uint8_t;
 using u16 = std::uint16_t;
@@ -212,3 +212,4 @@ enum WindowContent
     CONTENT_WINOUT = 2,
     CONTENT_WINOBJ = 3
 };
+
diff --git a/include/config.h b/include/config.h
index 7bb306f..125f34e 100644
--- a/include/config.h
+++ b/include/config.h
@@ -6,15 +6,39 @@
  * DATE: December 7th, 2020
  * DESCRIPTION: global configuration data for discovery
  */
+
 #pragma once
 
+#include <SDL2/SDL.h>
 #include <string>
 
+struct Keymap 
+{
+    SDL_Scancode gba_a;
+    SDL_Scancode gba_b;
+    SDL_Scancode gba_sel;
+    SDL_Scancode gba_start;
+    SDL_Scancode gba_dpad_right;
+    SDL_Scancode gba_dpad_left;
+    SDL_Scancode gba_dpad_up;
+    SDL_Scancode gba_dpad_down;
+    SDL_Scancode gba_r;
+    SDL_Scancode gba_l;
+};
+
 namespace config
 {
     extern std::string rom_name;
     extern std::string backup_path;
     extern std::string bios_name;
     extern bool show_help;
-    extern bool debug;
-}
\ No newline at end of file
+    extern bool debug; 
+    extern double framerate;
+
+    // handle config file
+    extern std::string config_file;
+    void read_config_file(void);
+
+    extern struct Keymap *keymap;
+};
+
diff --git a/include/dmath.h b/include/dmath.h
new file mode 100644
index 0000000..dfb1209
--- /dev/null
+++ b/include/dmath.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <cmath>
+#include <complex>
+#include <vector>
+#include "common.h"
+
+namespace dmath
+{
+  std::vector<std::complex<double>> fourier(std::vector<std::complex<double>>);
+};
diff --git a/include/log.h b/include/log.h
index d343581..2c817d5 100644
--- a/include/log.h
+++ b/include/log.h
@@ -10,7 +10,6 @@
 #pragma once
 
 #include "common.h"
-
 #include <fmt/format.h>
 #include <fmt/color.h>
 
diff --git a/include/mmio.h b/include/mmio.h
index 88861d3..fe843d8 100644
--- a/include/mmio.h
+++ b/include/mmio.h
@@ -119,4 +119,4 @@ constexpr u32 WAITCNT         = 0x4000204; // waitstate control
 constexpr u32 REG_IME         = 0x4000208; // master interrupt enable
 
 // GBA System control
-constexpr u32 REG_HALTCNT     = 0x4000301;
\ No newline at end of file
+constexpr u32 REG_HALTCNT     = 0x4000301;
diff --git a/include/util.h b/include/util.h
index 189cee2..5e49d0c 100644
--- a/include/util.h
+++ b/include/util.h
@@ -9,8 +9,8 @@
 
 #pragma once
 
-#include "common.h"
 #include <string>
+#include "common.h"
 
 using std::string;
 
@@ -23,8 +23,27 @@ namespace util
     ThumbInstruction getInstructionFormat(u16);
 
     // test if path exists
-    bool pathExists(string const &);
+    bool pathExists(std::string const &);
+
+    /**
+     * get subset of bits for purposes like destination register, opcode, shifts
+     * All instructions have data hidden within their codes;
+     * ex: A branch instruction holds the offset in bits [23-0]
+     * This function will extract the bits.
+     * Since the reference I am using is in reverse bit order, end >= start must be true
+     * 
+     * ex: bitseq<7, 4>(0b11110000) = 0b1111
+     */
+    template <int end, int start>
+    inline u32 bitseq(u32);
+
+    template <int end, int start>
+    inline u16 bitseq(u16);
+
+    inline s8 signum(double);
+
+    inline u32 secondsToSamples(double);
+};
 
-    // util inline functions
-    #include "util.inl"
-}
+// util inline functions
+#include "util.inl"
diff --git a/include/util.inl b/include/util.inl
index 36acf1e..f78b1fd 100644
--- a/include/util.inl
+++ b/include/util.inl
@@ -7,32 +7,37 @@
  * ex: bitseq<7, 4>(0b11110000) = 0b1111
  */
 template <int end, int start>
-inline u32 bitseq(u32 val)
+inline u32 util::bitseq(u32 val)
 {
-	if (end < start)
-		return 0;
+	  if (end < start)
+		    return 0;
 
-	static u32 mask = ~0;
+	  static u32 mask = ~0;
     val &= mask >> (31 - end);
     val >>= start;
     return val;
 }
 
 template <int end, int start>
-inline u16 bitseq(u16 val)
+inline u16 util::bitseq(u16 val)
 {
-	if (end < start)
+	  if (end < start)
 		return 0;
 
-	static u16 mask = ~0;
+  	static u16 mask = ~0;
     val &= mask >> (15 - end);
     val >>= start;
     return val;
 }
 
-inline s8 signum(double val) 
+inline s8 util::signum(double val) 
 {
     if(std::isnan(val)) throw std::invalid_argument("Invalid argument passed to util::signum");
     else return (s8) (0. < val) - (val < 0.);
 }
 
+inline u32 util::secondsToSamples(double s) 
+{
+    return s / 44100.0;
+}
+
diff --git a/src/APU.cpp b/src/APU.cpp
index 99b6578..f94f331 100644
--- a/src/APU.cpp
+++ b/src/APU.cpp
@@ -12,6 +12,7 @@
 #include <cstring>
 #include <iostream>
 #include "APU.h"
+#include "log.h"
 
 constexpr int AMPLITUDE   = 5000;
 constexpr int SAMPLE_RATE = 48000;
@@ -21,21 +22,21 @@ constexpr int BUFFER_SIZE = 2048;
  * SDL audio callback
  * @param userdata pointer to instance of APU
  * @param stream pointer to the audio data buffer to be filled
- * @param len length of that buffer in bytes
+ * @param len length of that buffein bytes
  */
 void callback(void *userdata, u8 *stream, int len)
 {
     APU *apu = reinterpret_cast<APU*>(userdata);
-	s16 *snd = reinterpret_cast<s16*>(stream);
+    s16 *snd = reinterpret_cast<s16*>(stream);
 
     // zero stream
     std::memset(stream, 0, len);
 
     s32 merged_stream_data;
-	for(int i = 0; i < len / 2; i++)
-	{
+    for(int i = 0; i < len / 2; i++)
+    {
         merged_stream_data = 0;
-        for (int c = 0; c < 4; c++)
+        for (int c = 0; c < 3; c++)
         {
             auto &channel = apu->channel[c];
             if (!channel.empty())
@@ -45,7 +46,7 @@ void callback(void *userdata, u8 *stream, int len)
             }
         }
         snd[i] = merged_stream_data;
-	}
+    }
 }
 
 APU::APU(AudioStat *stat) :
@@ -98,8 +99,9 @@ void APU::bufferChannel1()
     SDL_LockAudioDevice(driver_id);
     auto &chan = channel[0];
 
-    while (!chan.empty())
-        chan.pop();
+    while (!chan.empty()) {
+            chan.pop();
+    }
     
     int samples_buffered = 0;
 
@@ -168,12 +170,7 @@ void APU::bufferChannel1()
 
     while (1)
     {
-        // make sure we don't overflow the buffer
-        // TODO - find out if there's an actual reason the buffer is being overflowed
-        if (chan.size() >= 10000)
-            break;
-
-        samples_buffered++;
+       samples_buffered++;
         
         if (current_step == 0)
             break;
@@ -196,12 +193,19 @@ void APU::bufferChannel1()
         else
             volume = AMPLITUDE;
 
-        //// push samples according to wave cycle
-        for (int i = 0; i < lo; i++)
-            chan.push(volume);
-        for (int i = 0; i < hi; i++)
-            chan.push(-volume);
-       
+        // push samples according to wave cycle
+        // if max play time has elapsed, fill buffer with silence
+        for (int i = 0; i < lo; i++) 
+        {
+            if(timed && time_elapsed >= max_time) chan.push(0);
+            else chan.push(volume);
+        }
+        for (int i = 0; i < hi; i++) 
+        {
+            if(timed && time_elapsed >= max_time) chan.push(0);
+            else chan.push(-volume);
+        }
+      
         // sweep shift envelope 
         if (sweep_enabled && time_since_last_sweep_step >= sweep_time)
         {
@@ -228,10 +232,6 @@ void APU::bufferChannel1()
         time_since_last_env_step += static_cast<float>(period) / SAMPLE_RATE;
         time_since_last_sweep_step += static_cast<float>(period) / SAMPLE_RATE;
 
-        // time has elapsed longer than the sound should be played for
-        if (timed && time_elapsed >= max_time)
-            break;
-
         if (env_enabled && time_since_last_env_step >= step_time)
         {
             if (stat->sndcnt1_h.env_mode)
@@ -246,7 +246,7 @@ void APU::bufferChannel1()
         if (samples_buffered > 1000)
             break;
     }
-    stat->sndcnt1_x.reset = 0;
+
     SDL_UnlockAudioDevice(driver_id);
 }
 
@@ -258,7 +258,7 @@ void APU::bufferChannel2()
     SDL_LockAudioDevice(driver_id);
     auto &chan = channel[1];
 
-    while (!chan.empty())
+    while (!chan.empty()) 
         chan.pop();
     
     int samples_buffered = 0;
@@ -321,11 +321,18 @@ void APU::bufferChannel2()
         if (current_step == 0)
             break;
 
-        for (int i = 0; i < lo; i++)
-            chan.push(volume);
-        
-        for (int i = 0; i < hi; i++)
-            chan.push(-volume);
+        // push samples according to wave cycle
+        // if max play time has elapsed, fill buffer with silence
+        for (int i = 0; i < lo; i++) 
+        {
+            if(timed && time_elapsed >= max_time) chan.push(0);
+            else chan.push(volume);
+        }
+        for (int i = 0; i < hi; i++) 
+        {
+            if(timed && time_elapsed >= max_time) chan.push(0);
+            else chan.push(-volume);
+        }
         
         time_elapsed += static_cast<float>(period) / SAMPLE_RATE;
         time_since_last_env_step += static_cast<float>(period) / SAMPLE_RATE;
@@ -357,7 +364,7 @@ void APU::bufferChannel3()
     SDL_LockAudioDevice(driver_id);
     auto &chan = channel[2];
 
-    while (!chan.empty())
+    while (!chan.empty()) 
         chan.pop();
     
     auto reg_freq_to_hz = [](int reg_freq) -> float
diff --git a/src/Arm7.cpp b/src/Arm7.cpp
index ca9c3da..d34a734 100644
--- a/src/Arm7.cpp
+++ b/src/Arm7.cpp
@@ -679,7 +679,7 @@ void Arm7::updateCPSR(u32 value, bool flags_only)
         log(LogLevel::Warning, "Software is changing T-Bit in CPSR!\n");
 
     // validate CPSR wasn't given an invalid state
-    assert(getMode());
+    // assert(getMode());
 
     // if (sr.state == IRQ && registers.cpsr.i == 1) return; // irq disabled bit set
     // if (sr.state == FIQ && registers.cpsr.f == 1) return; // fiq disabled bit set
@@ -1301,40 +1301,36 @@ bool Arm7::checkState()
 }
 
 void Arm7::print() {
-    std::cout<< std::hex <<"R0 : 0x" << std::setw(8) << std::setfill('0') << getRegister(0) << 
-				" -- R4  : 0x" << std::setw(8) << std::setfill('0') << getRegister(4) << 
-				" -- R8  : 0x" << std::setw(8) << std::setfill('0') << getRegister(8) << 
-				" -- R12 : 0x" << std::setw(8) << std::setfill('0') << getRegister(12) << "\n";
-
-			std::cout<< std::hex <<"R1 : 0x" << std::setw(8) << std::setfill('0') << getRegister(1) << 
-				" -- R5  : 0x" << std::setw(8) << std::setfill('0') << getRegister(5) << 
-				" -- R9  : 0x" << std::setw(8) << std::setfill('0') << getRegister(9) << 
-				" -- R13 : 0x" << std::setw(8) << std::setfill('0') << getRegister(13) << "\n";
-
-			std::cout<< std::hex <<"R2 : 0x" << std::setw(8) << std::setfill('0') << getRegister(2) << 
-				" -- R6  : 0x" << std::setw(8) << std::setfill('0') << getRegister(6) << 
-				" -- R10 : 0x" << std::setw(8) << std::setfill('0') << getRegister(10) << 
-				" -- R14 : 0x" << std::setw(8) << std::setfill('0') << getRegister(14) << "\n";
-
-			std::cout<< std::hex <<"R3 : 0x" << std::setw(8) << std::setfill('0') << getRegister(3) << 
-				" -- R7  : 0x" << std::setw(8) << std::setfill('0') << getRegister(7) << 
-				" -- R11 : 0x" << std::setw(8) << std::setfill('0') << getRegister(11) << 
-				" -- R15 : 0x" << std::setw(8) << std::setfill('0') << getRegister(15) << "\n";
-
-	
-			std::cout<< std::hex <<"CPSR : 0x" << std::setw(8) << std::setfill('0') << registers.cpsr.raw << "\t";
-            if (getConditionCodeFlag(ConditionFlag::N))
-                std::cout << "N";
-            if (getConditionCodeFlag(ConditionFlag::Z))
-                std::cout << "Z";
-            if (getConditionCodeFlag(ConditionFlag::C))
-                std::cout << "C";
-            if (getConditionCodeFlag(ConditionFlag::V))
-                std::cout << "V";
-            std::cout << "\n";
-            //std:: cout << std::dec << ii << " instructions\n";
-    }
-
-// #include "HandlerArm.cpp"
-// #include "HandlerThumb.cpp"
-// #include "swi.cpp"
\ No newline at end of file
+std::cout<< std::hex <<"R0 : 0x" << std::setw(8) << std::setfill('0') << getRegister(0) << 
+            " -- R4  : 0x" << std::setw(8) << std::setfill('0') << getRegister(4) << 
+            " -- R8  : 0x" << std::setw(8) << std::setfill('0') << getRegister(8) << 
+            " -- R12 : 0x" << std::setw(8) << std::setfill('0') << getRegister(12) << "\n";
+
+        std::cout<< std::hex <<"R1 : 0x" << std::setw(8) << std::setfill('0') << getRegister(1) << 
+            " -- R5  : 0x" << std::setw(8) << std::setfill('0') << getRegister(5) << 
+            " -- R9  : 0x" << std::setw(8) << std::setfill('0') << getRegister(9) << 
+            " -- R13 : 0x" << std::setw(8) << std::setfill('0') << getRegister(13) << "\n";
+
+        std::cout<< std::hex <<"R2 : 0x" << std::setw(8) << std::setfill('0') << getRegister(2) << 
+            " -- R6  : 0x" << std::setw(8) << std::setfill('0') << getRegister(6) << 
+            " -- R10 : 0x" << std::setw(8) << std::setfill('0') << getRegister(10) << 
+            " -- R14 : 0x" << std::setw(8) << std::setfill('0') << getRegister(14) << "\n";
+
+        std::cout<< std::hex <<"R3 : 0x" << std::setw(8) << std::setfill('0') << getRegister(3) << 
+            " -- R7  : 0x" << std::setw(8) << std::setfill('0') << getRegister(7) << 
+            " -- R11 : 0x" << std::setw(8) << std::setfill('0') << getRegister(11) << 
+            " -- R15 : 0x" << std::setw(8) << std::setfill('0') << getRegister(15) << "\n";
+
+
+        std::cout<< std::hex <<"CPSR : 0x" << std::setw(8) << std::setfill('0') << registers.cpsr.raw << "\t";
+        if (getConditionCodeFlag(ConditionFlag::N))
+            std::cout << "N";
+        if (getConditionCodeFlag(ConditionFlag::Z))
+            std::cout << "Z";
+        if (getConditionCodeFlag(ConditionFlag::C))
+            std::cout << "C";
+        if (getConditionCodeFlag(ConditionFlag::V))
+            std::cout << "V";
+        std::cout << "\n";
+        //std:: cout << std::dec << ii << " instructions\n";
+}
diff --git a/src/Discovery.cpp b/src/Discovery.cpp
index 2a9dfa8..5ba1261 100644
--- a/src/Discovery.cpp
+++ b/src/Discovery.cpp
@@ -16,6 +16,7 @@
 #include "IRQ.h"
 #include "config.h"
 #include "audio_stat.h"
+#include "log.h"
 
 // global IRQ handler
 IRQ *irq;
@@ -33,6 +34,8 @@ Discovery::Discovery()
     cpu       = new Arm7(mem);
     ppu       = new PPU(mem, stat, scheduler);
     irq       = new IRQ();
+
+    config::read_config_file();
 }
 
 // parse command line args
@@ -43,36 +46,40 @@ void Discovery::parseArgs()
         // ROM name
         if (i == 0 && util::pathExists(argv[i]))
             config::rom_name = argv[i];
-		else if ((argv[i] == "-i" || argv[i] == "--input") && i != argv.size() -1)
-			config::rom_name = argv[++i];
-        else if ((argv[i] == "-b" || argv[i] == "--bios") && i != argv.size() - 1)
+    	else if ((argv[i] == "-i" || argv[i] == "--input") && i != argv.size()-1)
+		    config::rom_name = argv[++i];
+        else if ((argv[i] == "-b" || argv[i] == "--bios") && i != argv.size()-1)
             config::bios_name = argv[++i];
-		else if ((argv[i] == "-h" || argv[i] == "--help") && i == 0)
-			config::show_help = true;
+        else if ((argv[i] == "-c" || argv[i] == "--config") && i != argv.size()-1)
+            config::config_file = argv[++i];
+		    else if ((argv[i] == "-h" || argv[i] == "--help") && i == 0)
+			    config::show_help = true;
     }
 }
 
 void Discovery::printArgHelp()
 {
-	log("Usage:\n");
-	log("./discovery ./path/to/rom.gba\n");
-	log("\n");
-	log("Flags:\n");
-	log("-i, --input\n");
-	log("  Specifies input file for rom\n");
-	log("-b, --bios\n");
-	log("  Specifies GBA bios file\n");
-	log("-h, --help\n");
-	log("  Show help...\n");
+    log("Usage:\n");
+    log("discovery path/to/rom.gba\n");
+    log("\n");
+    log("Flags:\n");
+    log("-i, --input\n");
+    log("  Specifies input file for rom\n");
+    log("-b, --bios\n");
+    log("  Specifies GBA bios file, default is 'gba_bios.bin'\n");
+    log("-c, --config\n");
+    log("  Specifies config file, default is 'discovery.config'\n");
+    log("-h, --help\n");
+  	log("  Show help...\n");
 }
 
 void Discovery::shutdown()
 {
-    //SDL_PauseAudioDevice(1, 1);
+    // SDL_PauseAudioDevice(1, 1);
     // free resources and shutdown
 	delete cpu;
     delete ppu;
-    //delete apu;
+    // delete apu;
     delete mem;
     delete stat;
     delete gamepad;
@@ -101,7 +108,7 @@ void Discovery::frame()
         cpu->fetch();
         cpu->decode();
         cycles_elapsed = cpu->execute(cpu->pipeline[0].opcode);
-        //scheduler->advance(cycles_elapsed);
+        // scheduler->advance(cycles_elapsed);
 
         cpu->handleInterrupt();
 
diff --git a/src/Gamepad.cpp b/src/Gamepad.cpp
index 6e82d7b..71691cb 100644
--- a/src/Gamepad.cpp
+++ b/src/Gamepad.cpp
@@ -9,6 +9,7 @@
  */
 #include "Gamepad.h"
 #include "IRQ.h"
+#include "config.h"
 
 extern IRQ *irq;
 
@@ -32,16 +33,16 @@ void Gamepad::poll()
     //SDL_PumpEvents();
     auto *state = SDL_GetKeyboardState(nullptr);
 
-    keys.a     = state[SDL_SCANCODE_X]         ? 0 : 1;
-    keys.b     = state[SDL_SCANCODE_Z]         ? 0 : 1;
-    keys.sel   = state[SDL_SCANCODE_BACKSPACE] ? 0 : 1;
-    keys.start = state[SDL_SCANCODE_RETURN]    ? 0 : 1;
-    keys.right = state[SDL_SCANCODE_RIGHT]     ? 0 : 1;
-    keys.left  = state[SDL_SCANCODE_LEFT]      ? 0 : 1;
-    keys.up    = state[SDL_SCANCODE_UP]        ? 0 : 1;
-    keys.down  = state[SDL_SCANCODE_DOWN]      ? 0 : 1;
-    keys.r     = state[SDL_SCANCODE_S]         ? 0 : 1;
-    keys.l     = state[SDL_SCANCODE_A]         ? 0 : 1;
+    keys.a     = state[config::keymap->gba_a]              ? 0 : 1;
+    keys.b     = state[config::keymap->gba_b]              ? 0 : 1;
+    keys.sel   = state[config::keymap->gba_sel]            ? 0 : 1;
+    keys.start = state[config::keymap->gba_start]          ? 0 : 1;
+    keys.right = state[config::keymap->gba_dpad_right]     ? 0 : 1;
+    keys.left  = state[config::keymap->gba_dpad_left]      ? 0 : 1;
+    keys.up    = state[config::keymap->gba_dpad_up]        ? 0 : 1;
+    keys.down  = state[config::keymap->gba_dpad_down]      ? 0 : 1;
+    keys.r     = state[config::keymap->gba_r]              ? 0 : 1;
+    keys.l     = state[config::keymap->gba_l]              ? 0 : 1;
 
     if (keycnt.irq) // key interrupts enabled
         checkInterrupt();
diff --git a/src/Memory.cpp b/src/Memory.cpp
index 026007d..86f2738 100644
--- a/src/Memory.cpp
+++ b/src/Memory.cpp
@@ -42,7 +42,7 @@ Memory::Memory(LcdStat *stat, Timer *timer, Gamepad *gamepad, AudioStat *audio_s
 Memory::~Memory()
 {
     // dump cart ram contents to backup file
-    backup->writeChip();    
+    backup->writeChip();
 }
 
 void Memory::reset()
@@ -329,7 +329,6 @@ void Memory::write16(u32 address, u16 value)
 
 void Memory::write8(u32 address, u8 value)
 {
-
     switch (address >> 24)
     {
         case 0x0:
@@ -411,7 +410,7 @@ void Memory::write8(u32 address, u8 value)
     //game rom
     if (address >= MEM_SIZE)
     {
-        //std::cerr << "Warning: writing to game rom\n";
+        // std::cerr << "Warning: writing to game rom\n";
         cart_rom[address - MEM_SIZE] = value;
         // std::cerr << "Done\n";
         return;
@@ -655,7 +654,7 @@ void Memory::write8(u32 address, u8 value)
         
         // REG_SOUND1CNT_X
         case REG_SOUND1CNT_X:
-        case REG_SOUND1CNT_X + 1:
+        case REG_SOUND1CNT_X + 1: 
             audio_stat->sndcnt1_x.raw = (memory[REG_SOUND1CNT_X + 1] << 8) | (memory[REG_SOUND1CNT_X]);
             apu->bufferChannel1();
             break;
@@ -678,14 +677,14 @@ void Memory::write8(u32 address, u8 value)
         case REG_SOUND3CNT_L:
         case REG_SOUND3CNT_L + 1:
             audio_stat->sndcnt3_l.raw = (memory[REG_SOUND3CNT_L + 1] << 8) | (memory[REG_SOUND3CNT_L]);
-            apu->bufferChannel3();
+            // apu->bufferChannel3();
             break;
 
         // REG_SOUND3CNT_H
         case REG_SOUND3CNT_H:
         case REG_SOUND3CNT_H + 1:
             audio_stat->sndcnt3_h.raw = (memory[REG_SOUND3CNT_H + 1] << 8) | (memory[REG_SOUND3CNT_H]);
-            apu->bufferChannel3();
+            // apu->bufferChannel3();
             break;
         
         // REG_SOUND3CNT_X
@@ -909,6 +908,7 @@ void Memory::write8(u32 address, u8 value)
             irq->setIME(memory[REG_IME + 1] << 8 | memory[REG_IME]);
             break;
     }
+
 }
 
 u32 Memory::read32Unsafe(u32 address)
diff --git a/src/PPU.cpp b/src/PPU.cpp
index 16c0203..3730be8 100644
--- a/src/PPU.cpp
+++ b/src/PPU.cpp
@@ -13,6 +13,7 @@
 #include "PPU.h"
 #include "util.h"
 #include "IRQ.h"
+#include "log.h"
 
 extern IRQ *irq;
 
@@ -178,7 +179,6 @@ void PPU::tick()
 void PPU::render()
 {
     //std::cout << "Executing graphics mode: " << (int) (stat->dispcnt.mode) << "\n";
-
     
 }
 
@@ -529,7 +529,7 @@ void PPU::renderScanlineBitmap(int mode)
             if (stat->dispcnt.ps)
                 pal_ptr += 0xA000;
 
-            for (int x = 0; x < 160; +x)
+            for (int x = 0; x < 160; ++x)
             {
                 // multiply by 2 because each entry in palram is 2 bytes
                 palette_index = vram[pal_ptr++] * 2;
@@ -838,4 +838,4 @@ inline bool PPU::isInWindow(int win, int x, int y)
     return (x >= stat->winh[win].left) && (x < stat->winh[win].right) && (y >= stat->winv[win].top) && (y < stat->winv[win].bottom);
 }
 
-inline u32 PPU::u16ToU32Color(u16 color_u16) { return color_lut[color_u16 & 0x7FFF]; }
\ No newline at end of file
+inline u32 PPU::u16ToU32Color(u16 color_u16) { return color_lut[color_u16 & 0x7FFF]; }
diff --git a/src/Timer.cpp b/src/Timer.cpp
index 160689d..db26bca 100644
--- a/src/Timer.cpp
+++ b/src/Timer.cpp
@@ -9,6 +9,7 @@
 
 #include "Timer.h"
 #include "IRQ.h"
+#include "log.h"
 
 extern IRQ *irq;
 
@@ -113,4 +114,33 @@ void Timer::cascade(int ch)
         }
             
     }
-}
\ No newline at end of file
+}
+
+// void Timer::overflow(int ch)
+// {   
+//     auto &tmr = channel[ch];
+//     tmr.data = tmr.reload;
+
+//     // overflow irq
+//     if (tmr.irq)
+//     {
+//         log("Timer {} IRQ\n", ch);
+        
+//         switch (ch)
+//         {
+//             case 0: irq->raise(InterruptOccasion::TIMER0); break;
+//             case 1: irq->raise(InterruptOccasion::TIMER1); break;
+//             case 2: irq->raise(InterruptOccasion::TIMER2); break;
+//             case 3: irq->raise(InterruptOccasion::TIMER3); break;
+//         }
+//     }
+
+//     tmr.cycle_started = scheduler->cycles;
+
+//     // add next overflow event to scheduler
+//     int cycles_until_overflow = (0xFFFF - tmr.data) * tmr.prescalar;
+//     scheduler->add(cycles_until_overflow, tmr.onOverflow, ch);
+
+//     // cascade
+//     cascade(ch);
+// }
diff --git a/src/config.cpp b/src/config.cpp
index ce94f9c..ca5d0ae 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -2,17 +2,148 @@
  * License: GPLv2
  * See LICENSE.txt for full license text
  * 
- * FILE: config.h
+ * FILE: config.cpp
  * DATE: December 7th, 2020
  * DESCRIPTION: global configuration data for discovery
  */
+
+#include <fstream>
+#include <regex>
+#include <vector>
+#include <map>
+#include <exception>
+#include <algorithm>
 #include "config.h" 
+#include "Discovery.h"
+
+std::map<std::string, SDL_Scancode> KeyboardInput = 
+{
+    {
+        { "a", SDL_SCANCODE_A },
+        { "b", SDL_SCANCODE_B },
+        { "c", SDL_SCANCODE_C },
+        { "d", SDL_SCANCODE_D },
+        { "e", SDL_SCANCODE_E },
+        { "f", SDL_SCANCODE_F },
+        { "g", SDL_SCANCODE_G },
+        { "h", SDL_SCANCODE_H },
+        { "i", SDL_SCANCODE_I },
+        { "j", SDL_SCANCODE_J },
+        { "k", SDL_SCANCODE_K },
+        { "l", SDL_SCANCODE_L },
+        { "m", SDL_SCANCODE_M },
+        { "n", SDL_SCANCODE_N },
+        { "o", SDL_SCANCODE_O },
+        { "p", SDL_SCANCODE_P },
+        { "q", SDL_SCANCODE_Q },
+        { "r", SDL_SCANCODE_R },
+        { "s", SDL_SCANCODE_S },
+        { "t", SDL_SCANCODE_T },
+        { "u", SDL_SCANCODE_U },
+        { "v", SDL_SCANCODE_V },
+        { "w", SDL_SCANCODE_W },
+        { "x", SDL_SCANCODE_X },
+        { "y", SDL_SCANCODE_Y },
+        { "z", SDL_SCANCODE_Z },
+        { "cr", SDL_SCANCODE_RETURN },
+        { "bs", SDL_SCANCODE_BACKSPACE },
+        { "right", SDL_SCANCODE_RIGHT },
+        { "left", SDL_SCANCODE_LEFT },
+        { "up", SDL_SCANCODE_UP },
+        { "down", SDL_SCANCODE_DOWN },
+        { "space", SDL_SCANCODE_SPACE },
+        { "tab", SDL_SCANCODE_TAB },
+        { "rshift", SDL_SCANCODE_RSHIFT },
+        { "lshift", SDL_SCANCODE_LSHIFT },
+        { "rctrl", SDL_SCANCODE_RCTRL },
+        { "lctrl", SDL_SCANCODE_LCTRL },
+        { ",", SDL_SCANCODE_COMMA },
+        { ".", SDL_SCANCODE_PERIOD }
+    }
+};
 
-namespace config
+namespace config 
 {
+    // default config values
     std::string rom_name = "";
     std::string backup_path = "";
     std::string bios_name = "gba_bios.bin";
     bool show_help = false;
     bool debug = false;
-}
\ No newline at end of file
+    double framerate = 0.;
+
+    // default config file
+    std::string config_file = "discovery.config";
+
+    // define default keymap
+    struct Keymap *keymap = new Keymap {
+        gba_a: KeyboardInput["x"],
+        gba_b: KeyboardInput["z"],
+        gba_sel: KeyboardInput["bs"],
+        gba_start: KeyboardInput["cr"],
+        gba_dpad_right: KeyboardInput["right"],
+        gba_dpad_left: KeyboardInput["left"],
+        gba_dpad_up: KeyboardInput["up"],
+        gba_dpad_down: KeyboardInput["down"],
+        gba_r: KeyboardInput["s"],
+        gba_l: KeyboardInput["a"]
+    };
+}
+
+void config::read_config_file()
+{
+    try 
+    {
+        std::ifstream file;
+        std::map<std::string, std::string> config;
+        file.open(config_file, std::ios::binary);
+        
+        // read lines in config file
+        if(file.fail())
+            throw std::runtime_error("Could not read Discovery config file.");
+        if(file.is_open())
+        {
+            std::string line;
+            std::regex reg("^\\s*([^\\W][\\w]*)\\s*=\\s*(<?[^\\W\\s][\\w]*\\S*>?)|(#{1,})+2.*$");
+            std::smatch group;
+
+            while(std::getline(file, line)) 
+            {
+                if(std::regex_search(line, group, reg))  
+                {
+                    if(group.size()) 
+                        config.insert({group[1].str(), group[2].str()});
+                    else
+                        log(LogLevel::Error, "Error parsing config file.");
+                }
+            }
+        }
+        file.close();
+        
+        // validate and set key/value pair
+        for(auto it = config.begin(); it != config.end(); it++)
+        {
+            std::string key = it->first, val = it->second;
+            auto keymap_code = KeyboardInput.find(val);
+            if(keymap_code != KeyboardInput.end())
+            {
+                if(key == "gba_a") keymap->gba_a = keymap_code->second;
+                else if(key == "gba_b") keymap->gba_b = keymap_code->second;
+                else if(key == "gba_sel") keymap->gba_sel = keymap_code->second;
+                else if(key == "gba_start") keymap->gba_start = keymap_code->second;
+                else if(key == "gba_dpad_right") keymap->gba_dpad_right = keymap_code->second;
+                else if(key == "gba_dpad_left") keymap->gba_dpad_left = keymap_code->second;
+                else if(key == "gba_dpad_up") keymap->gba_dpad_up = keymap_code->second;
+                else if(key == "gba_dpad_down") keymap->gba_dpad_down = keymap_code->second;
+                else if(key == "gba_r") keymap->gba_r = keymap_code->second;
+                else if(key == "gba_r") keymap->gba_l = keymap_code->second;
+            }
+        }
+    } 
+    catch(std::exception &e)
+    {
+        // handle no config file
+        log(LogLevel::Warning, "Could not read Discovery config file.");
+    }
+}
+
diff --git a/src/dmath.cpp b/src/dmath.cpp
new file mode 100644
index 0000000..da74037
--- /dev/null
+++ b/src/dmath.cpp
@@ -0,0 +1,34 @@
+#include <iostream>
+#include "dmath.h"
+
+/**
+ * fourier transform
+ */
+std::vector<std::complex<double>> dmath::fourier(std::vector<std::complex<double>> x) {
+  size_t size = x.size();
+  if(size <= 1) return x;
+
+  // divide by even / odd index values
+  std::vector<std::complex<double>> evens, odds;
+  for(u16 i = 0; i < size; i++) {
+    if(i % 2) {
+      odds.push_back(x[i]);
+    } else {
+      evens.push_back(x[i]);
+    }
+  }
+
+  // solve recursively
+  evens = dmath::fourier(evens);
+  odds = dmath::fourier(odds);
+
+  // merge
+  std::vector<std::complex<double>> merged(x);
+  for(size_t i = 0; i < size / 2; ++i) {
+    std::complex<double> t = std::polar(1., -2 * M_PI * ( i / size )) * odds[i];
+    merged[i] = evens[i] + t;
+    merged[i+(size/2)] = evens[i] - t;
+  }
+  return merged;
+}
+
diff --git a/src/main.cpp b/src/main.cpp
index 7c94db8..814c37e 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -44,7 +44,6 @@ int main(int argc, char **argv)
     // load bios, rom, and launch game loop
     emulator.mem->loadBios(config::bios_name);
     emulator.mem->loadRom(config::rom_name);
-    
 
     bool running = true;
     SDL_Event e;
@@ -61,6 +60,7 @@ int main(int argc, char **argv)
 
         // draw final_screen pixels on screen
         SDL_UpdateWindowSurface(window);
+        // std::cout << frame << "\n";
         
         // calculate fps
         if (++frame == 60)
@@ -71,6 +71,7 @@ int main(int argc, char **argv)
             clock_t new_time = std::clock();
             duration = (new_time - old_time) / (double) CLOCKS_PER_SEC;
             old_time = new_time;
+            config::framerate = 60. / duration;
 
             std::stringstream stream;
             stream << std::fixed << std::setprecision(1) << (60 / duration);
@@ -83,17 +84,38 @@ int main(int argc, char **argv)
 
         while (SDL_PollEvent(&e))
         {
-            // Click X on window
-            if (e.type == SDL_QUIT)
-                running = false;
-        
-            // Key press event
-            if (e.type == SDL_KEYDOWN || e.type == SDL_KEYUP)
+            switch(e.type)
             {
-                if (e.key.keysym.sym == SDLK_ESCAPE)
+                case SDL_QUIT:
+                    // Click X on window
                     running = false;
-
-                emulator.gamepad->poll();
+                    break;
+                case SDL_KEYDOWN: [[fallthrough]]
+                case SDL_KEYUP:
+                    // Key press event
+                    if (e.key.keysym.sym == SDLK_ESCAPE)
+                        running = false;                     
+                    emulator.gamepad->poll();
+                    break;
+                case SDL_WINDOWEVENT:
+                    if(e.window.event == SDL_WINDOWEVENT_RESIZED)
+                    {
+                        int width = e.window.data1, height = e.window.data2;
+                        float real_rat = (float) width / (float) height;
+                        float gbas_rat = (float) SCREEN_WIDTH / (float) SCREEN_HEIGHT;
+                        float prop = real_rat / gbas_rat;
+                        float ratw = prop > 1.0f ? height*gbas_rat : width;
+                        float rath = prop > 1.0f ? height : height*prop;
+                        float cx = prop > 1.0f ? (width-ratw)/2 : 0;
+                        float cy = prop > 1.0f ? 0: (height-rath)/2;
+                        SDL_SetWindowSize(window, width, height);
+                        final_screen = SDL_GetWindowSurface(window);
+                        scale_rect.w = ratw;
+                        scale_rect.h = rath;
+                        scale_rect.x = cx;
+                        scale_rect.y = cy;
+                        SDL_BlitScaled(original_screen, nullptr, final_screen, &scale_rect);
+                    }
             }
         }
     }
@@ -107,9 +129,9 @@ int main(int argc, char **argv)
 
 void init()
 {
-    assert(SDL_Init(SDL_INIT_VIDEO) >= 0);
+    // assert(SDL_Init(SDL_INIT_VIDEO) >= 0);
 
-    window = SDL_CreateWindow("discovery", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH * 2, SCREEN_HEIGHT * 2, 0);
+    window = SDL_CreateWindow("discovery", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH * 2, SCREEN_HEIGHT * 2, SDL_WINDOW_RESIZABLE);
     assert(window);
 
     final_screen = SDL_GetWindowSurface(window);
@@ -119,4 +141,5 @@ void init()
     scale_rect.h = SCREEN_HEIGHT * 2;
     scale_rect.x = 0;
     scale_rect.y = 0;
-}
\ No newline at end of file
+}
+
diff --git a/src/util.cpp b/src/util.cpp
index ad8dbbc..c5bb099 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -61,7 +61,7 @@ ArmInstruction util::getInstructionFormat(u32 instruction)
             if ((instruction >> 4 & 0xF) == 0x9)
             {
                 if (instruction & 0x2000000) // 25th bit is 1
-                    return ArmInstruction::DP; 
+                    return ArmInstruction::DP;
                 else if (((instruction >> 23) & 0x3) == 0x2) // bits 24-23 are 10
                     return ArmInstruction::SWP;
                 else if (instruction & 0x800000) // 23rd bit is 1
diff --git a/third_party/fmt b/third_party/fmt
index 018688d..061e364 160000
--- a/third_party/fmt
+++ b/third_party/fmt
@@ -1 +1 @@
-Subproject commit 018688da2a58ba25cdf173bd899734f755adb11a
+Subproject commit 061e364b25b5e5ca7cf50dd25282892922375ddc