diff --git a/crates/molotov-gui/src/app.rs b/crates/molotov-gui/src/app.rs
new file mode 100644
index 0000000..46591b8
--- /dev/null
+++ b/crates/molotov-gui/src/app.rs
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+use eframe::egui;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Tab {
+    Play,
+    FastFlags,
+    Mods,
+    Audio,
+    MultiInstance,
+    Maintenance,
+}
+
+pub struct MolotovApp {
+    current_tab: Tab,
+    pub safe_mode: bool,
+    pub fps_cap: i64,
+    pub vram_skip_mips: bool,
+}
+
+impl Default for MolotovApp {
+    fn default() -> Self {
+        Self {
+            current_tab: Tab::Play,
+            safe_mode: false,
+            fps_cap: 144,
+            vram_skip_mips: false,
+        }
+    }
+}
+
+impl MolotovApp {
+    pub fn active_tab_name(&self) -> &'static str {
+        match self.current_tab {
+            Tab::Play => "Play",
+            Tab::FastFlags => "FastFlags",
+            Tab::Mods => "Mods",
+            Tab::Audio => "Audio & Voice",
+            Tab::MultiInstance => "Instances",
+            Tab::Maintenance => "Maintenance",
+        }
+    }
+}
+
+impl eframe::App for MolotovApp {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        egui::TopBottomPanel::top("top_panel").show(ctx, |ui| {
+            ui.horizontal(|ui| {
+                ui.selectable_value(&mut self.current_tab, Tab::Play, "🎮 Play");
+                ui.selectable_value(&mut self.current_tab, Tab::FastFlags, "⚙️ FastFlags");
+                ui.selectable_value(&mut self.current_tab, Tab::Mods, "🎨 Mods");
+                ui.selectable_value(&mut self.current_tab, Tab::Audio, "🎙️ Audio");
+                ui.selectable_value(&mut self.current_tab, Tab::MultiInstance, "👥 Instances");
+                ui.selectable_value(&mut self.current_tab, Tab::Maintenance, "🧹 Maintenance");
+            });
+        });
+
+        egui::CentralPanel::default().show(ctx, |ui| match self.current_tab {
+            Tab::Play => {
+                ui.heading("Molotov Roblox Runtime");
+                ui.checkbox(&mut self.safe_mode, "Safe Mode (Minimal Flags)");
+                if ui.button("🚀 Launch Roblox").clicked() {
+                    println!("Launch clicked!");
+                }
+            }
+            Tab::FastFlags => {
+                ui.heading("Performance & FastFlags");
+                ui.add(egui::Slider::new(&mut self.fps_cap, 30..=360).text("Target FPS"));
+                ui.checkbox(&mut self.vram_skip_mips, "Reduce VRAM Texture Mipmaps (NVIDIA fix)");
+            }
+            Tab::Mods => {
+                ui.heading("Asset Mods (In-Memory)");
+                ui.label("Drop custom ouch.ogg or cursors into ~/.config/molotov/mods/");
+            }
+            Tab::Audio => {
+                ui.heading("PipeWire Voice Chat");
+                ui.label("Microphone active stream is destroyed on pause to prevent indicator leaks.");
+            }
+            Tab::MultiInstance => {
+                ui.heading("Multi-Instance Sandboxing (bubblewrap)");
+                ui.label("Launch isolated accounts in independent namespaces.");
+            }
+            Tab::Maintenance => {
+                ui.heading("Maintenance & Cleaning");
+                if ui.button("Clean Stale Versions").clicked() {
+                    println!("Clean clicked!");
+                }
+            }
+        });
+    }
+}
diff --git a/crates/molotov-gui/src/lib.rs b/crates/molotov-gui/src/lib.rs
index 6d9dd2e..68c18f6 100644
--- a/crates/molotov-gui/src/lib.rs
+++ b/crates/molotov-gui/src/lib.rs
@@ -1,4 +1,19 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
+pub mod app;
+use app::MolotovApp;
+
 pub fn run() {
-    println!("Molotov GUI placeholder");
+    let native_options = eframe::NativeOptions {
+        viewport: eframe::egui::ViewportBuilder::default()
+            .with_inner_size([720.0, 480.0])
+            .with_min_inner_size([600.0, 400.0])
+            .with_title("Molotov - Roblox Runtime for Linux"),
+        ..Default::default()
+    };
+
+    let _ = eframe::run_native(
+        "Molotov",
+        native_options,
+        Box::new(|_cc| Ok(Box::new(MolotovApp::default()))),
+    );
 }
diff --git a/crates/molotov-gui/tests/gui_test.rs b/crates/molotov-gui/tests/gui_test.rs
new file mode 100644
index 0000000..c5f21d1
--- /dev/null
+++ b/crates/molotov-gui/tests/gui_test.rs
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+use molotov_gui::app::MolotovApp;
+
+#[test]
+fn test_gui_default_tab_is_play() {
+    let app = MolotovApp::default();
+    assert_eq!(app.active_tab_name(), "Play");
+}