diff --git a/Cargo.toml b/Cargo.toml
index 6b20561..34f9e60 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,7 @@ members = [
     "crates/voltex_ai",
     "crates/voltex_net",
     "crates/voltex_script",
+    "crates/voltex_editor",
 ]
 
 [workspace.dependencies]
@@ -35,6 +36,7 @@ voltex_audio = { path = "crates/voltex_audio" }
 voltex_ai = { path = "crates/voltex_ai" }
 voltex_net = { path = "crates/voltex_net" }
 voltex_script = { path = "crates/voltex_script" }
+voltex_editor = { path = "crates/voltex_editor" }
 wgpu = "28.0"
 winit = "0.30"
 bytemuck = { version = "1", features = ["derive"] }
diff --git a/crates/voltex_editor/Cargo.toml b/crates/voltex_editor/Cargo.toml
new file mode 100644
index 0000000..cbe80b7
--- /dev/null
+++ b/crates/voltex_editor/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "voltex_editor"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bytemuck = { workspace = true }
diff --git a/crates/voltex_editor/src/draw_list.rs b/crates/voltex_editor/src/draw_list.rs
new file mode 100644
index 0000000..51fce06
--- /dev/null
+++ b/crates/voltex_editor/src/draw_list.rs
@@ -0,0 +1,123 @@
+use bytemuck::{Pod, Zeroable};
+use crate::font::FontAtlas;
+
+#[repr(C)]
+#[derive(Copy, Clone, Debug, Pod, Zeroable)]
+pub struct DrawVertex {
+    pub position: [f32; 2],
+    pub uv: [f32; 2],
+    pub color: [u8; 4],
+}
+
+pub struct DrawCommand {
+    pub index_offset: u32,
+    pub index_count: u32,
+}
+
+pub struct DrawList {
+    pub vertices: Vec<DrawVertex>,
+    pub indices: Vec<u16>,
+    pub commands: Vec<DrawCommand>,
+}
+
+impl DrawList {
+    pub fn new() -> Self {
+        DrawList {
+            vertices: Vec::new(),
+            indices: Vec::new(),
+            commands: Vec::new(),
+        }
+    }
+
+    pub fn clear(&mut self) {
+        self.vertices.clear();
+        self.indices.clear();
+        self.commands.clear();
+    }
+
+    /// Add a solid-color rectangle. UV is (0,0) for solid color rendering.
+    pub fn add_rect(&mut self, x: f32, y: f32, w: f32, h: f32, color: [u8; 4]) {
+        self.add_rect_uv(x, y, w, h, 0.0, 0.0, 0.0, 0.0, color);
+    }
+
+    /// Add a textured quad with explicit UV coordinates.
+    pub fn add_rect_uv(
+        &mut self,
+        x: f32, y: f32, w: f32, h: f32,
+        u0: f32, v0: f32, u1: f32, v1: f32,
+        color: [u8; 4],
+    ) {
+        let index_offset = self.indices.len() as u32;
+        let base_vertex = self.vertices.len() as u16;
+
+        // 4 vertices: top-left, top-right, bottom-right, bottom-left
+        self.vertices.push(DrawVertex { position: [x,     y    ], uv: [u0, v0], color });
+        self.vertices.push(DrawVertex { position: [x + w, y    ], uv: [u1, v0], color });
+        self.vertices.push(DrawVertex { position: [x + w, y + h], uv: [u1, v1], color });
+        self.vertices.push(DrawVertex { position: [x,     y + h], uv: [u0, v1], color });
+
+        // 2 triangles = 6 indices
+        self.indices.push(base_vertex);
+        self.indices.push(base_vertex + 1);
+        self.indices.push(base_vertex + 2);
+        self.indices.push(base_vertex);
+        self.indices.push(base_vertex + 2);
+        self.indices.push(base_vertex + 3);
+
+        self.commands.push(DrawCommand {
+            index_offset,
+            index_count: 6,
+        });
+    }
+
+    /// Add text at the given position. One quad per character, using glyph UVs from the atlas.
+    pub fn add_text(&mut self, font: &FontAtlas, text: &str, x: f32, y: f32, color: [u8; 4]) {
+        let gw = font.glyph_width as f32;
+        let gh = font.glyph_height as f32;
+        let mut cx = x;
+        for ch in text.chars() {
+            let (u0, v0, u1, v1) = font.glyph_uv(ch);
+            self.add_rect_uv(cx, y, gw, gh, u0, v0, u1, v1, color);
+            cx += gw;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::font::FontAtlas;
+
+    #[test]
+    fn test_add_rect_vertex_index_count() {
+        let mut dl = DrawList::new();
+        dl.add_rect(0.0, 0.0, 100.0, 50.0, [255, 0, 0, 255]);
+        assert_eq!(dl.vertices.len(), 4);
+        assert_eq!(dl.indices.len(), 6);
+        assert_eq!(dl.commands.len(), 1);
+        assert_eq!(dl.commands[0].index_count, 6);
+        assert_eq!(dl.commands[0].index_offset, 0);
+    }
+
+    #[test]
+    fn test_add_text_char_count() {
+        let font = FontAtlas::generate();
+        let mut dl = DrawList::new();
+        let text = "Hello";
+        dl.add_text(&font, text, 0.0, 0.0, [255, 255, 255, 255]);
+        // 5 chars => 5 quads => 5*4=20 vertices, 5*6=30 indices
+        assert_eq!(dl.vertices.len(), 5 * 4);
+        assert_eq!(dl.indices.len(), 5 * 6);
+        assert_eq!(dl.commands.len(), 5);
+    }
+
+    #[test]
+    fn test_clear() {
+        let mut dl = DrawList::new();
+        dl.add_rect(0.0, 0.0, 50.0, 50.0, [0, 0, 0, 255]);
+        dl.clear();
+        assert!(dl.vertices.is_empty());
+        assert!(dl.indices.is_empty());
+        assert!(dl.commands.is_empty());
+    }
+}
diff --git a/crates/voltex_editor/src/font.rs b/crates/voltex_editor/src/font.rs
new file mode 100644
index 0000000..8ea2852
--- /dev/null
+++ b/crates/voltex_editor/src/font.rs
@@ -0,0 +1,135 @@
+/// Bitmap font atlas for ASCII 32-126.
+/// 8x12 pixel glyphs arranged in 16 columns x 6 rows = 128x72 texture.
+pub struct FontAtlas {
+    pub width: u32,
+    pub height: u32,
+    pub glyph_width: u32,
+    pub glyph_height: u32,
+    pub pixels: Vec<u8>, // R8 grayscale
+}
+
+impl FontAtlas {
+    /// Generate a minimal font atlas.
+    /// Each glyph is 8x12 pixels. Atlas is 16 cols x 6 rows = 128x72.
+    /// Space (32) = all zeros. Other chars get a simple recognizable pattern.
+    pub fn generate() -> Self {
+        let glyph_width: u32 = 8;
+        let glyph_height: u32 = 12;
+        let cols: u32 = 16;
+        let rows: u32 = 6;
+        let width = cols * glyph_width;   // 128
+        let height = rows * glyph_height; // 72
+
+        let mut pixels = vec![0u8; (width * height) as usize];
+
+        // ASCII 32 (space) through 126 (~) = 95 characters
+        for code in 32u8..=126u8 {
+            let index = (code - 32) as u32;
+            let col = index % cols;
+            let row = index / cols;
+            let base_x = col * glyph_width;
+            let base_y = row * glyph_height;
+
+            if code == 32 {
+                // Space: all zeros (already zero)
+                continue;
+            }
+
+            // Generate a recognizable pattern based on char code.
+            // Draw a border frame + inner pattern derived from code value.
+            for py in 0..glyph_height {
+                for px in 0..glyph_width {
+                    let pixel_idx = ((base_y + py) * width + (base_x + px)) as usize;
+
+                    let on_border = px == 0 || px == glyph_width - 1
+                        || py == 0 || py == glyph_height - 1;
+
+                    // Inner pattern: use bits of char code to create variation
+                    let inner_bit = ((code as u32).wrapping_mul(px + 1).wrapping_mul(py + 1)) & 0x3;
+                    let on_inner = inner_bit == 0 && px > 1 && px < glyph_width - 2
+                        && py > 2 && py < glyph_height - 2;
+
+                    // Horizontal bar in middle for letter-like appearance
+                    let mid_y = glyph_height / 2;
+                    let on_midbar = py == mid_y && px > 1 && px < glyph_width - 2;
+
+                    // Vertical stem on left side
+                    let on_stem = px == 2 && py > 1 && py < glyph_height - 2;
+
+                    if on_border || on_inner || on_midbar || on_stem {
+                        pixels[pixel_idx] = 255;
+                    }
+                }
+            }
+        }
+
+        FontAtlas {
+            width,
+            height,
+            glyph_width,
+            glyph_height,
+            pixels,
+        }
+    }
+
+    /// Returns (u0, v0, u1, v1) UV coordinates for a given character.
+    /// Returns coordinates for space if character is out of ASCII range.
+    pub fn glyph_uv(&self, ch: char) -> (f32, f32, f32, f32) {
+        let code = ch as u32;
+        let index = if code >= 32 && code <= 126 {
+            code - 32
+        } else {
+            0 // space
+        };
+
+        let cols = self.width / self.glyph_width;
+        let col = index % cols;
+        let row = index / cols;
+
+        let u0 = (col * self.glyph_width) as f32 / self.width as f32;
+        let v0 = (row * self.glyph_height) as f32 / self.height as f32;
+        let u1 = u0 + self.glyph_width as f32 / self.width as f32;
+        let v1 = v0 + self.glyph_height as f32 / self.height as f32;
+
+        (u0, v0, u1, v1)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_generate_size() {
+        let atlas = FontAtlas::generate();
+        assert_eq!(atlas.width, 128);
+        assert_eq!(atlas.height, 72);
+        assert_eq!(atlas.pixels.len(), (128 * 72) as usize);
+    }
+
+    #[test]
+    fn test_glyph_uv_space() {
+        let atlas = FontAtlas::generate();
+        let (u0, v0, u1, v1) = atlas.glyph_uv(' ');
+        assert!((u0 - 0.0).abs() < 1e-6);
+        assert!((v0 - 0.0).abs() < 1e-6);
+        assert!((u1 - 8.0 / 128.0).abs() < 1e-6);
+        assert!((v1 - 12.0 / 72.0).abs() < 1e-6);
+    }
+
+    #[test]
+    fn test_glyph_uv_a() {
+        let atlas = FontAtlas::generate();
+        // 'A' = ASCII 65, index = 65 - 32 = 33
+        // col = 33 % 16 = 1, row = 33 / 16 = 2
+        let (u0, v0, u1, v1) = atlas.glyph_uv('A');
+        let expected_u0 = 1.0 * 8.0 / 128.0;
+        let expected_v0 = 2.0 * 12.0 / 72.0;
+        let expected_u1 = expected_u0 + 8.0 / 128.0;
+        let expected_v1 = expected_v0 + 12.0 / 72.0;
+        assert!((u0 - expected_u0).abs() < 1e-6, "u0 mismatch: {} vs {}", u0, expected_u0);
+        assert!((v0 - expected_v0).abs() < 1e-6, "v0 mismatch: {} vs {}", v0, expected_v0);
+        assert!((u1 - expected_u1).abs() < 1e-6);
+        assert!((v1 - expected_v1).abs() < 1e-6);
+    }
+}
diff --git a/crates/voltex_editor/src/layout.rs b/crates/voltex_editor/src/layout.rs
new file mode 100644
index 0000000..6d3ac75
--- /dev/null
+++ b/crates/voltex_editor/src/layout.rs
@@ -0,0 +1,32 @@
+/// Simple cursor-based layout state for immediate mode UI.
+pub struct LayoutState {
+    pub cursor_x: f32,
+    pub cursor_y: f32,
+    pub indent: f32,
+    pub line_height: f32,
+    pub padding: f32,
+}
+
+impl LayoutState {
+    /// Create a new layout state starting at (x, y).
+    pub fn new(x: f32, y: f32) -> Self {
+        LayoutState {
+            cursor_x: x,
+            cursor_y: y,
+            indent: x,
+            line_height: 12.0,
+            padding: 4.0,
+        }
+    }
+
+    /// Advance to the next line: cursor_y += line_height + padding, cursor_x = indent.
+    pub fn advance_line(&mut self) {
+        self.cursor_y += self.line_height + self.padding;
+        self.cursor_x = self.indent;
+    }
+
+    /// Advance horizontally: cursor_x += width + padding.
+    pub fn advance_x(&mut self, width: f32) {
+        self.cursor_x += width + self.padding;
+    }
+}
diff --git a/crates/voltex_editor/src/lib.rs b/crates/voltex_editor/src/lib.rs
new file mode 100644
index 0000000..8fef481
--- /dev/null
+++ b/crates/voltex_editor/src/lib.rs
@@ -0,0 +1,10 @@
+pub mod font;
+pub mod draw_list;
+pub mod layout;
+pub mod ui_context;
+pub mod widgets;
+
+pub use font::FontAtlas;
+pub use draw_list::{DrawVertex, DrawCommand, DrawList};
+pub use layout::LayoutState;
+pub use ui_context::UiContext;
diff --git a/crates/voltex_editor/src/ui_context.rs b/crates/voltex_editor/src/ui_context.rs
new file mode 100644
index 0000000..8212718
--- /dev/null
+++ b/crates/voltex_editor/src/ui_context.rs
@@ -0,0 +1,81 @@
+use crate::draw_list::DrawList;
+use crate::font::FontAtlas;
+use crate::layout::LayoutState;
+
+pub struct UiContext {
+    pub hot: Option<u64>,
+    pub active: Option<u64>,
+    pub draw_list: DrawList,
+    pub layout: LayoutState,
+    pub mouse_x: f32,
+    pub mouse_y: f32,
+    pub mouse_down: bool,
+    pub mouse_clicked: bool,
+    pub mouse_released: bool,
+    pub screen_width: f32,
+    pub screen_height: f32,
+    pub font: FontAtlas,
+    id_counter: u64,
+    prev_mouse_down: bool,
+}
+
+impl UiContext {
+    /// Create a new UiContext for the given screen dimensions.
+    pub fn new(screen_w: f32, screen_h: f32) -> Self {
+        UiContext {
+            hot: None,
+            active: None,
+            draw_list: DrawList::new(),
+            layout: LayoutState::new(0.0, 0.0),
+            mouse_x: 0.0,
+            mouse_y: 0.0,
+            mouse_down: false,
+            mouse_clicked: false,
+            mouse_released: false,
+            screen_width: screen_w,
+            screen_height: screen_h,
+            font: FontAtlas::generate(),
+            id_counter: 0,
+            prev_mouse_down: false,
+        }
+    }
+
+    /// Begin a new frame: clear draw list, reset id counter, update mouse state.
+    pub fn begin_frame(&mut self, mx: f32, my: f32, mouse_down: bool) {
+        self.draw_list.clear();
+        self.id_counter = 0;
+        self.hot = None;
+
+        self.mouse_x = mx;
+        self.mouse_y = my;
+
+        // Compute transitions
+        self.mouse_clicked = !self.prev_mouse_down && mouse_down;
+        self.mouse_released = self.prev_mouse_down && !mouse_down;
+
+        self.mouse_down = mouse_down;
+        self.prev_mouse_down = mouse_down;
+
+        // Reset layout to top-left
+        self.layout = LayoutState::new(0.0, 0.0);
+    }
+
+    /// End the current frame.
+    pub fn end_frame(&mut self) {
+        // Nothing for now — GPU submission will hook in here later.
+    }
+
+    /// Generate a new unique ID for this frame.
+    pub fn gen_id(&mut self) -> u64 {
+        self.id_counter += 1;
+        self.id_counter
+    }
+
+    /// Check if the mouse cursor is inside the given rectangle.
+    pub fn mouse_in_rect(&self, x: f32, y: f32, w: f32, h: f32) -> bool {
+        self.mouse_x >= x
+            && self.mouse_x < x + w
+            && self.mouse_y >= y
+            && self.mouse_y < y + h
+    }
+}
diff --git a/crates/voltex_editor/src/widgets.rs b/crates/voltex_editor/src/widgets.rs
new file mode 100644
index 0000000..bc2c647
--- /dev/null
+++ b/crates/voltex_editor/src/widgets.rs
@@ -0,0 +1,281 @@
+use crate::ui_context::UiContext;
+
+// Color palette
+const COLOR_BG: [u8; 4]             = [0x2B, 0x2B, 0x2B, 0xFF];
+const COLOR_BUTTON: [u8; 4]         = [0x44, 0x44, 0x44, 0xFF];
+const COLOR_BUTTON_HOT: [u8; 4]     = [0x55, 0x55, 0x55, 0xFF];
+const COLOR_BUTTON_ACTIVE: [u8; 4]  = [0x66, 0x66, 0x66, 0xFF];
+const COLOR_TEXT: [u8; 4]           = [0xEE, 0xEE, 0xEE, 0xFF];
+const COLOR_PANEL: [u8; 4]          = [0x33, 0x33, 0x33, 0xFF];
+const COLOR_SLIDER_BG: [u8; 4]      = [0x44, 0x44, 0x44, 0xFF];
+const COLOR_SLIDER_HANDLE: [u8; 4]  = [0x88, 0x88, 0xFF, 0xFF];
+const COLOR_CHECK_BG: [u8; 4]       = [0x44, 0x44, 0x44, 0xFF];
+const COLOR_CHECK_MARK: [u8; 4]     = [0x88, 0xFF, 0x88, 0xFF];
+
+impl UiContext {
+    /// Draw text at the current cursor position and advance to the next line.
+    pub fn text(&mut self, text: &str) {
+        let x = self.layout.cursor_x;
+        let y = self.layout.cursor_y;
+        // We need to clone font info for the borrow checker
+        let gw = self.font.glyph_width as f32;
+        let gh = self.font.glyph_height as f32;
+
+        // Draw each character
+        let mut cx = x;
+        for ch in text.chars() {
+            let (u0, v0, u1, v1) = self.font.glyph_uv(ch);
+            self.draw_list.add_rect_uv(cx, y, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+            cx += gw;
+        }
+
+        self.layout.advance_line();
+    }
+
+    /// Draw a button with the given label. Returns true if clicked this frame.
+    pub fn button(&mut self, label: &str) -> bool {
+        let id = self.gen_id();
+        let gw = self.font.glyph_width as f32;
+        let gh = self.font.glyph_height as f32;
+        let padding = self.layout.padding;
+
+        let text_w = label.len() as f32 * gw;
+        let btn_w = text_w + padding * 2.0;
+        let btn_h = gh + padding * 2.0;
+
+        let x = self.layout.cursor_x;
+        let y = self.layout.cursor_y;
+
+        let hovered = self.mouse_in_rect(x, y, btn_w, btn_h);
+
+        if hovered {
+            self.hot = Some(id);
+            if self.mouse_down {
+                self.active = Some(id);
+            }
+        }
+
+        // Determine color
+        let bg_color = if self.active == Some(id) && hovered {
+            COLOR_BUTTON_ACTIVE
+        } else if self.hot == Some(id) {
+            COLOR_BUTTON_HOT
+        } else {
+            COLOR_BUTTON
+        };
+
+        // Draw background rect
+        self.draw_list.add_rect(x, y, btn_w, btn_h, bg_color);
+
+        // Draw text centered inside button
+        let text_x = x + padding;
+        let text_y = y + padding;
+        let mut cx = text_x;
+        for ch in label.chars() {
+            let (u0, v0, u1, v1) = self.font.glyph_uv(ch);
+            self.draw_list.add_rect_uv(cx, text_y, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+            cx += gw;
+        }
+
+        self.layout.advance_line();
+
+        // Return true if mouse was released over this button while it was active
+        let clicked = hovered && self.mouse_released && self.active == Some(id);
+        if self.mouse_released {
+            if self.active == Some(id) {
+                self.active = None;
+            }
+        }
+        clicked
+    }
+
+    /// Draw a horizontal slider. Returns the (possibly new) value after interaction.
+    pub fn slider(&mut self, label: &str, value: f32, min: f32, max: f32) -> f32 {
+        let id = self.gen_id();
+        let gw = self.font.glyph_width as f32;
+        let gh = self.font.glyph_height as f32;
+        let padding = self.layout.padding;
+
+        let slider_w = 150.0_f32;
+        let slider_h = gh + padding * 2.0;
+        let handle_w = 10.0_f32;
+
+        let x = self.layout.cursor_x;
+        let y = self.layout.cursor_y;
+
+        let hovered = self.mouse_in_rect(x, y, slider_w, slider_h);
+
+        if hovered && self.mouse_clicked {
+            self.active = Some(id);
+        }
+
+        let mut new_value = value;
+
+        if self.active == Some(id) {
+            if self.mouse_down {
+                // Map mouse_x to value
+                let t = ((self.mouse_x - x - handle_w / 2.0) / (slider_w - handle_w)).clamp(0.0, 1.0);
+                new_value = min + t * (max - min);
+            } else if self.mouse_released {
+                self.active = None;
+            }
+        }
+
+        // Clamp value
+        new_value = new_value.clamp(min, max);
+
+        // Draw background bar
+        self.draw_list.add_rect(x, y, slider_w, slider_h, COLOR_SLIDER_BG);
+
+        // Draw handle
+        let t = if (max - min).abs() < 1e-6 {
+            0.0
+        } else {
+            (new_value - min) / (max - min)
+        };
+        let handle_x = x + t * (slider_w - handle_w);
+        self.draw_list.add_rect(handle_x, y, handle_w, slider_h, COLOR_SLIDER_HANDLE);
+
+        // Draw label to the right of the slider
+        let label_x = x + slider_w + padding;
+        let label_y = y + padding;
+        let mut cx = label_x;
+        for ch in label.chars() {
+            let (u0, v0, u1, v1) = self.font.glyph_uv(ch);
+            self.draw_list.add_rect_uv(cx, label_y, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+            cx += gw;
+        }
+
+        self.layout.advance_line();
+
+        new_value
+    }
+
+    /// Draw a checkbox. Returns the new checked state (toggled on click).
+    pub fn checkbox(&mut self, label: &str, checked: bool) -> bool {
+        let id = self.gen_id();
+        let gw = self.font.glyph_width as f32;
+        let gh = self.font.glyph_height as f32;
+        let padding = self.layout.padding;
+
+        let box_size = gh;
+        let x = self.layout.cursor_x;
+        let y = self.layout.cursor_y;
+
+        let hovered = self.mouse_in_rect(x, y, box_size + padding + label.len() as f32 * gw, gh + padding);
+
+        if hovered {
+            self.hot = Some(id);
+        }
+
+        let mut new_checked = checked;
+        if hovered && self.mouse_clicked {
+            new_checked = !checked;
+        }
+
+        // Draw checkbox background
+        self.draw_list.add_rect(x, y, box_size, box_size, COLOR_CHECK_BG);
+
+        // Draw check mark if checked
+        if new_checked {
+            let inner = 3.0;
+            self.draw_list.add_rect(
+                x + inner,
+                y + inner,
+                box_size - inner * 2.0,
+                box_size - inner * 2.0,
+                COLOR_CHECK_MARK,
+            );
+        }
+
+        // Draw label
+        let label_x = x + box_size + padding;
+        let label_y = y;
+        let mut cx = label_x;
+        for ch in label.chars() {
+            let (u0, v0, u1, v1) = self.font.glyph_uv(ch);
+            self.draw_list.add_rect_uv(cx, label_y, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+            cx += gw;
+        }
+
+        self.layout.advance_line();
+
+        new_checked
+    }
+
+    /// Begin a panel: draw background and title, set cursor inside panel.
+    pub fn begin_panel(&mut self, title: &str, x: f32, y: f32, w: f32, h: f32) {
+        let gh = self.font.glyph_height as f32;
+        let padding = self.layout.padding;
+
+        // Draw panel background
+        self.draw_list.add_rect(x, y, w, h, COLOR_PANEL);
+
+        // Draw title bar (slightly darker background handled by same panel color here)
+        let title_bar_h = gh + padding * 2.0;
+        self.draw_list.add_rect(x, y, w, title_bar_h, COLOR_BG);
+
+        // Draw title text
+        let gw = self.font.glyph_width as f32;
+        let mut cx = x + padding;
+        let ty = y + padding;
+        for ch in title.chars() {
+            let (u0, v0, u1, v1) = self.font.glyph_uv(ch);
+            self.draw_list.add_rect_uv(cx, ty, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+            cx += gw;
+        }
+
+        // Set cursor to inside the panel (below title bar)
+        self.layout = crate::layout::LayoutState::new(x + padding, y + title_bar_h + padding);
+    }
+
+    /// End a panel — currently a no-op; cursor remains where it was.
+    pub fn end_panel(&mut self) {
+        // Nothing for now; future could restore outer cursor state.
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::ui_context::UiContext;
+
+    #[test]
+    fn test_button_returns_false_when_not_clicked() {
+        let mut ctx = UiContext::new(800.0, 600.0);
+        // Mouse is at (500, 500) — far from any button
+        ctx.begin_frame(500.0, 500.0, false);
+        let result = ctx.button("Click Me");
+        assert!(!result, "button should return false when mouse is not over it");
+    }
+
+    #[test]
+    fn test_button_returns_true_when_clicked() {
+        let mut ctx = UiContext::new(800.0, 600.0);
+
+        // Frame 1: mouse over button, pressed down
+        // Button will be at layout cursor (0, 0) with some width/height
+        // glyph_width=8, "OK"=2 chars, btn_w = 2*8 + 4*2 = 24, btn_h = 12 + 4*2 = 20
+        ctx.begin_frame(10.0, 5.0, true);
+        let _ = ctx.button("OK");
+
+        // Frame 2: mouse still over button, released
+        ctx.begin_frame(10.0, 5.0, false);
+        let result = ctx.button("OK");
+        assert!(result, "button should return true when clicked and released");
+    }
+
+    #[test]
+    fn test_slider_returns_clamped_value() {
+        let mut ctx = UiContext::new(800.0, 600.0);
+        ctx.begin_frame(0.0, 0.0, false);
+
+        // Value above max should be clamped
+        let v = ctx.slider("test", 150.0, 0.0, 100.0);
+        assert!((v - 100.0).abs() < 1e-6, "slider should clamp to max: got {}", v);
+
+        ctx.begin_frame(0.0, 0.0, false);
+        // Value below min should be clamped
+        let v2 = ctx.slider("test", -10.0, 0.0, 100.0);
+        assert!((v2 - 0.0).abs() < 1e-6, "slider should clamp to min: got {}", v2);
+    }
+}