diff --git a/Cargo.lock b/Cargo.lock
index 89a1a80..48a7d2d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -938,9 +938,9 @@ checksum = "bd0c93bb4b0c6d9b77f4435b0ae98c24d17f1c45b2ff844c6151a07256ca923b"
 
 [[package]]
 name = "dive-deco"
-version = "1.1.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "75463653535318f7ff3e93717bc63390a195179ad83b766a67a2939a360fb3cc"
+checksum = "3d2da424a210bb90c7550cc5c62a632c09c38c6549243b07089eed81906f86bd"
 
 [[package]]
 name = "dive-reporter"
diff --git a/src/app.rs b/src/app.rs
index 5013dc0..e74cce4 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -1,14 +1,34 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 
 use eframe::egui::{self, InnerResponse, Ui};
-use std::future::Future;
+use std::{future::Future, path::PathBuf};
+use std::error::Error;
 use rfd::FileDialog;
 use crate::{dive, stats::{Stats, StatsOutput}};
 
+#[derive(Clone)]
 pub struct App {
     title: String,
     stats: Stats,
     stats_output: StatsOutput,
+    config: AppConfig,
+    state: AppState,
+}
+
+#[derive(Clone)]
+struct AppState {
+    error: Option<AppError>
+}
+
+#[derive(Clone)]
+struct AppError {
+    text: String,
+}
+
+#[derive(Clone)]
+struct AppConfig {
+    path: Option<String>,
+    gradient_factors: (u8, u8),
 }
 
 impl Default for App {
@@ -17,6 +37,13 @@ impl Default for App {
             title: "Dive reporter".to_owned(),
             stats: Stats::new(),
             stats_output: vec![],
+            config: AppConfig {
+                path: None,
+                gradient_factors: (30, 70)
+            },
+            state: AppState {
+                error: None,
+            }
         }
     }
 }
@@ -25,30 +52,29 @@ impl eframe::App for App {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         egui::CentralPanel::default().show(ctx, |ui| {
             ui.heading(&self.title);
-            // a simple button opening the dialog
-            if ui.button("📂 Open UDDF file").clicked() {
-                let file = FileDialog::new()
-                .set_directory("/")
-                .pick_file();
+            ui.separator();
 
-                if let Some(file_path) = file {
-                    // todo err handling
-                    self.stats = Stats::new().from_path(file_path.to_str().unwrap()).unwrap();
-                }
-            }
+            // config
+            self.render_pair(ui, "Path:", &self.config.path.clone().unwrap_or("-".to_string()));
+            ui.separator();
 
-            let stats = &self.stats;
-            if stats.dives_no > 0 {
-                ui.vertical(|ui| {
-                    self.render_pair(ui, "Dives:", &stats.dives_no.to_string());
-                    self.render_pair(ui, "Total time:", &Stats::seconds_to_readable(stats.total_time));
-                    self.render_pair(ui, "Max depth", &stats.depth_max.to_string());
-                    self.render_pair(ui, "Deco dives:", &stats.deco_dives_no.to_string());
-                    self.render_pair(ui, "Total time in deco:", &&Stats::seconds_to_readable(stats.time_in_deco));
-                    self.render_pair(ui, "Max surface GF:", &stats.gf_surf_max.round().to_string());
-                    self.render_pair(ui, "Max GF99:", &stats.gf_99_max.round().to_string());
-                    self.render_pair(ui, "Max end GF:", &stats.gf_end_max.round().to_string());
-                });
+            // open file btn
+            self.render_file_btns(ui);
+
+            ui.separator();
+
+            // stats container
+            match &self.state.error {
+                None => {
+                    let stats = self.stats.clone();
+                    if stats.dives_no > 0 {
+                        self.state.error = None;
+                        self.render_stats(ui, &stats)
+                    }
+                },
+                Some(err) => {
+                    self.render_error(ui, &err);
+                }
             }
         });
     }
@@ -58,6 +84,8 @@ impl App {
     pub fn init(&self) -> Result<(), eframe::Error> {
         let options = eframe::NativeOptions {
             viewport: egui::ViewportBuilder::default().with_inner_size([300.0, 600.0]),
+            follow_system_theme: false,
+            default_theme: eframe::Theme::Dark,
             ..Default::default()
         };
         eframe::run_native(
@@ -69,10 +97,80 @@ impl App {
         )
     }
 
+    fn render_file_btns(&mut self, ui: &mut Ui) {
+        if ui.button("📂 Open UDDF file").clicked() {
+            let file = FileDialog::new()
+                .set_directory("/")
+                .pick_file();
+
+            if let Some(file_path) = file {
+                self.run_stats(&file_path);
+            }
+        }
+    }
+
+    fn render_stats(&mut self, ui: &mut Ui, stats: &Stats) {
+        let depth_max = stats.depth_max.to_string();
+        let gf_surf_max = stats.gf_surf_max.round().to_string();
+        let gf_99_max = stats.gf_99_max.round().to_string();
+        let gf_end_max = stats.gf_end_max.round().to_string();
+
+        ui.vertical(|ui| {
+            self.render_pair(ui, "Dives:", &stats.dives_no.to_string());
+            self.render_pair(ui, "Total time:", &Stats::seconds_to_readable(stats.total_time));
+            self.render_pair(ui, "Max depth", &format!("{depth_max}m"));
+            self.render_pair(ui, "Deco dives:", &stats.deco_dives_no.to_string());
+            self.render_pair(ui, "Total time in deco:", &Stats::seconds_to_readable(stats.time_in_deco));
+            self.render_pair(ui, "Max surface GF:", &format!("{gf_surf_max}%"));
+            self.render_pair(ui, "Max GF99:", &format!("{gf_99_max}%"));
+            self.render_pair(ui, "Max end GF:", &format!("{gf_end_max}%"));
+            self.render_pair(ui, "Time below:", "");
+            for record in stats.time_below.iter() {
+                let (depth, time) = record;
+                ui.indent("", |ui| {
+                    self.render_pair(ui, &format!("-{depth}:"), &Stats::seconds_to_readable(*time));
+                });
+            }
+        });
+    }
+
     pub fn render_pair(&self, ui: &mut Ui, v1: &str, v2: &str) -> InnerResponse<()> {
         ui.horizontal(|ui| {
             ui.label(v1);
             ui.label(v2);
         })
     }
+
+    fn render_error(&self, ui: &mut Ui, err: &AppError) {
+        let err_details_text = err.text.to_string();
+
+        ui.vertical(|ui| {
+            ui.heading("Error while reading stats");
+            ui.label(format!("Details: {err_details_text}"));
+        });
+    }
+
+    fn update_path(&mut self, new_path: String) {
+        self.config.path = Some(new_path);
+    }
+
+    fn run_stats(&mut self, file_path: &PathBuf) {
+        let selected_path = file_path.to_str().unwrap();
+        self.update_path(selected_path.to_string());
+        let stats_res = Stats::new().from_path(file_path.to_str().unwrap());
+        match stats_res {
+            Ok(stats) => {
+                if let Some(err) = &self.state.error {
+                    self.state.error = None;
+                }
+                self.stats = stats
+            },
+            Err(err) => {
+                let app_err = AppError {
+                    text: err.to_string()
+                };
+                self.state.error = Some(app_err);
+            }
+        }
+    }
 }
diff --git a/src/dive.rs b/src/dive.rs
index dd53a08..f1b1db7 100644
--- a/src/dive.rs
+++ b/src/dive.rs
@@ -1,4 +1,4 @@
-use dive_deco::{BuehlmannConfig, BuehlmannModel, DecoModel, Gas, Pressure};
+use dive_deco::{BuehlmannConfig, BuehlmannModel, DecoModel, Gas, Pressure, Supersaturation};
 
 use crate::common::{GradientFactorsSetting, GF};
 use crate::parser::WaypointElem;
@@ -105,8 +105,8 @@ impl Dive {
         model.step(&data_point.depth, &step_time, gas);
 
         // GFs
-        let gfs = model.gfs_current();
-        self.register_gfs(gfs, &step_time, &data_point.depth);
+        let Supersaturation { gf_99, gf_surf } = model.supersaturation();
+        self.register_gfs((gf_99, gf_surf), &step_time, &data_point.depth);
 
         // deco time
         if model.ceiling() > 0. {
diff --git a/src/stats.rs b/src/stats.rs
index c27cda8..488424d 100644
--- a/src/stats.rs
+++ b/src/stats.rs
@@ -4,8 +4,7 @@ use crate::parser::{self, UDDFDoc, Mix, DiveElem, WaypointElem};
 use crate::dive::{Dive, DiveConfig};
 use colored::*;
 
-#[derive(Debug)]
-
+#[derive(Clone, Debug)]
 pub struct Stats {
     pub dives_no: usize,
     pub total_time: Seconds,