diff --git a/src/sudoku.clj b/src/sudoku.clj
index 5254c46..1077153 100644
--- a/src/sudoku.clj
+++ b/src/sudoku.clj
@@ -3,56 +3,108 @@
 
 (def board identity)
 
+(def all-values #{1 2 3 4 5 6 7 8 9})
+
+(def all-indexes #{0 1 2 3 4 5 6 7 8})
+
 (defn value-at [board coord]
-  nil)
+  (get-in board coord))
 
 (defn has-value? [board coord]
-  nil)
+  ((complement zero?) (value-at board coord)))
 
 (defn row-values [board coord]
-  nil)
+  (let [[row col] coord]
+    (set (map #(value-at board [row %])
+              all-indexes))))
 
 (defn col-values [board coord]
-  nil)
+  (let [[row col] coord]
+    (set (map #(value-at board [% col])
+              all-indexes))))
 
-(defn coord-pairs [coords]
-  nil)
+(defn coord-pairs [coord-sequence]
+  (for [row coord-sequence
+        col coord-sequence]
+    [row col]))
 
 (defn block-values [board coord]
-  nil)
+  (let [[row col] coord
+        reducer (fn [x] (if (== 0 (mod x 3))
+                          x
+                          (recur (dec x))))
+        [top left] [(reducer row) (reducer col)]]
+    (set (for [r [0 1 2]
+               c [0 1 2]]
+           (value-at board 
+                     [(+ top r) (+ left c)])))))
 
 (defn valid-values-for [board coord]
-  nil)
+  (if (has-value? board coord)
+    #{}
+    (set/difference all-values (set/union (row-values board coord)
+                                          (col-values board coord)
+                                          (block-values board coord)))))
 
 (defn filled? [board]
-  nil)
+  (every? (partial has-value? board) 
+          (for [row all-indexes
+                col all-indexes]
+            [row col])))
 
 (defn rows [board]
-  nil)
+  (map (partial row-values board)
+       (for [row all-indexes]
+         [row 0])))
 
 (defn valid-rows? [board]
-  nil)
+  (every? (partial = all-values)
+          (rows board)))
 
 (defn cols [board]
-  nil)
+  (map (partial col-values board)
+       (for [col all-indexes]
+         [0 col])))
 
 (defn valid-cols? [board]
-  nil)
+  (every? (partial = all-values)
+          (cols board)))
 
 (defn blocks [board]
-  nil)
+  (map (partial block-values board)
+       (for [row [0 3 6]
+             col [0 3 6]]
+         [row col])))
 
 (defn valid-blocks? [board]
-  nil)
+  (every? (partial = all-values)
+          (blocks board)))
 
 (defn valid-solution? [board]
-  nil)
+  (and (valid-rows? board)
+       (valid-cols? board)
+       (valid-blocks? board)))
 
 (defn set-value-at [board coord new-value]
-  nil)
+  (assoc-in board coord new-value))
 
 (defn find-empty-point [board]
-  nil)
+  (let [all-coords (coord-pairs all-indexes)]
+    (first (drop-while (partial has-value? board)
+                       all-coords))))
+
+(defn solve-helper [board]
+  (if (filled? board)
+    (if (valid-solution? board)
+      [board]
+      [])
+    (let [coord (find-empty-point board)]
+      (for [value (valid-values-for board coord) 
+            solution (solve-helper (set-value-at board 
+                                                 coord 
+                                                 value))]
+        solution))))
 
 (defn solve [board]
-  nil)
+  (first (solve-helper board)))
+