diff --git a/game/commands.odin b/game/commands.odin
index 9869ce3..d3633e7 100644
--- a/game/commands.odin
+++ b/game/commands.odin
@@ -15,6 +15,9 @@ Command :: struct {
 }
 
 gather_commands :: proc(world: ^World) -> Command {
+	overlay_cmd := poll_overlay_command()
+	if overlay_cmd.kind != .None do return overlay_cmd
+
 	if world.phase == .Build && rl.IsKeyPressed(.N) {
 		return Command{kind = .Start_Wave}
 	}
@@ -25,12 +28,6 @@ gather_commands :: proc(world: ^World) -> Command {
 		return Command{kind = .Place_Tower, gx = gx, gy = gy}
 	}
 
-	if rl.IsMouseButtonPressed(.LEFT) {
-		mouse := rl.GetMousePosition()
-		gx, gy := screen_to_grid(mouse.x, mouse.y)
-		return Command{kind = .Place_Tower, gx = gx, gy = gy}
-	}
-
 	return Command{kind = .None}
 }
 
diff --git a/game/constants.odin b/game/constants.odin
index 176fd21..97c3a99 100644
--- a/game/constants.odin
+++ b/game/constants.odin
@@ -1,5 +1,7 @@
 package game
 
+import clay "../clay-odin"
+
 MAP_W :: 30 // map width in tiles
 MAP_H :: 20 // map height in tiles
 TILE_SIZE :: 32 // size of tiles in pixels
@@ -17,3 +19,9 @@ MAX_PROJECTILES :: 64
 PROJECTILE_SPEED :: 280 // pixels per second
 PROJECTILE_HIT_RADIUS :: 10
 
+UI_BAR_COLOR :: clay.Color{20, 40, 20, 200}
+UI_TEXT_COLOR :: clay.Color{240, 240, 230, 255}
+UI_GOLD_COLOR :: clay.Color{255, 215, 80, 255}
+UI_BUTTON_COLOR :: clay.Color{60, 120, 60, 255}
+UI_BUTTON_HOVER :: clay.Color{80, 150, 80, 255}
+
diff --git a/game/hud.odin b/game/hud.odin
deleted file mode 100644
index eb9623e..0000000
--- a/game/hud.odin
+++ /dev/null
@@ -1,50 +0,0 @@
-package game
-
-import clay "../clay-odin"
-import "core:fmt"
-import rl "vendor:raylib"
-
-UI_BAR_COLOR :: clay.Color{20, 40, 20, 200}
-UI_TEXT_COLOR :: clay.Color{240, 240, 230, 255}
-UI_GOLD_COLOR :: clay.Color{255, 215, 80, 255}
-
-ui_text_scratch: [64]u8
-
-build_hud :: proc(world: ^World) {
-	if clay.UI(clay.ID("HudBar"))(
-	{
-		layout = {
-			layoutDirection = .LeftToRight,
-			sizing = {width = clay.SizingGrow({}), height = clay.SizingFixed(28)},
-			padding = clay.PaddingAll(6),
-			childGap = 8,
-			childAlignment = {y = .Center},
-		},
-		backgroundColor = UI_BAR_COLOR,
-	},
-	) {
-		gold_text := fmt.bprintf(ui_text_scratch[:], "Gold: %d", world.gold)
-		clay.Text(
-			gold_text,
-			clay.TextElementConfig{textColor = UI_GOLD_COLOR, fontId = UI_FONT_ID, fontSize = 18},
-		)
-	}
-}
-
-render_hud :: proc(world: ^World) {
-	rl.DrawText(fmt.ctprintf("Base HP: %d", world.base_health), 10, 32, 22, rl.BLACK)
-	rl.DrawText(fmt.ctprintf("Enemies: %d", active_enemy_count(world)), 10, 54, 22, rl.BLACK)
-	rl.DrawText(fmt.ctprintf("Wave: %d / %d", world.wave, MAX_WAVES), 10, 76, 22, rl.BLACK)
-
-	switch world.phase {
-	case .Build:
-		rl.DrawText("Build - click towers, N = start wave", 10, 98, 22, rl.BLACK)
-	case .Combat:
-		rl.DrawText("Combat!", 10, 98, 22, rl.MAROON)
-	case .Game_Over:
-		rl.DrawText("GAME_OVER", 260, 280, 40, rl.RED)
-	case .Victory:
-		rl.DrawText("Victory!", 260, 280, 40, rl.GREEN)
-	}
-}
-
diff --git a/game/overlay.odin b/game/overlay.odin
new file mode 100644
index 0000000..48b1ef7
--- /dev/null
+++ b/game/overlay.odin
@@ -0,0 +1,89 @@
+package game
+
+import clay "../clay-odin"
+import "core:fmt"
+import rl "vendor:raylib"
+
+ui_hud_scratch: struct {
+	gold: [64]u8,
+	hp:   [64]u8,
+	wave: [64]u8,
+}
+
+build_overlay :: proc(world: ^World) {
+	if clay.UI(clay.ID("HudBar"))(
+	{
+		layout = {
+			layoutDirection = .LeftToRight,
+			sizing = {width = clay.SizingGrow({}), height = clay.SizingFixed(28)},
+			padding = clay.PaddingAll(6),
+			childGap = 8,
+			childAlignment = {y = .Center},
+		},
+		backgroundColor = UI_BAR_COLOR,
+	},
+	) {
+		gold_text := fmt.bprintf(ui_hud_scratch.gold[:], "Gold: %d", world.gold)
+		clay.Text(
+			gold_text,
+			clay.TextElementConfig{textColor = UI_GOLD_COLOR, fontId = UI_FONT_ID, fontSize = 18},
+		)
+
+		hp_text := fmt.bprintf(ui_hud_scratch.hp[:], "Base HP: %d", world.base_health)
+		clay.Text(
+			hp_text,
+			clay.TextElementConfig{textColor = UI_TEXT_COLOR, fontId = UI_FONT_ID, fontSize = 18},
+		)
+
+		wave_text := fmt.bprintf(ui_hud_scratch.wave[:], "Wave: %d / %d", world.wave, MAX_WAVES)
+		clay.Text(
+			wave_text,
+			clay.TextElementConfig{textColor = UI_TEXT_COLOR, fontId = UI_FONT_ID, fontSize = 18},
+		)
+
+		if world.phase == .Build {
+			if clay.UI(clay.ID("StartWaveBtn"))(
+			{
+				layout = {
+					sizing = {width = clay.SizingFixed(110), height = clay.SizingFixed(22)},
+					padding = clay.PaddingAll(4),
+					childAlignment = {x = .Center, y = .Center},
+				},
+				backgroundColor = clay.Hovered() ? UI_BUTTON_HOVER : UI_BUTTON_COLOR,
+			},
+			) {
+				clay.Text(
+					"Start Wave",
+					clay.TextElementConfig {
+						textColor = UI_TEXT_COLOR,
+						fontId = UI_FONT_ID,
+						fontSize = 16,
+					},
+				)
+			}
+		}
+	}
+}
+
+render_overlay :: proc(world: ^World) {
+	switch world.phase {
+	case .Build:
+	case .Combat:
+		rl.DrawText("Combat!", 10, 98, 22, rl.MAROON)
+	case .Game_Over:
+		rl.DrawText("GAME_OVER", 260, 280, 40, rl.RED)
+	case .Victory:
+		rl.DrawText("Victory!", 260, 280, 40, rl.GREEN)
+	}
+}
+
+poll_overlay_command :: proc() -> Command {
+	if clay.PointerOver(clay.ID("StartWaveBtn")) {
+		ptr := clay.GetPointerState()
+		if ptr.state == .PressedThisFrame {
+			return Command{kind = .Start_Wave}
+		}
+	}
+	return Command{kind = .None}
+}
+
diff --git a/game/render.odin b/game/render.odin
index 708e026..dc3fe1b 100644
--- a/game/render.odin
+++ b/game/render.odin
@@ -5,5 +5,6 @@ render_world :: proc(world: ^World) {
 	render_enemies(world)
 	render_towers(world)
 	render_projectiles(world)
+	render_overlay(world)
 }
 
diff --git a/game/ui.odin b/game/ui.odin
index 95ebe2f..14af682 100644
--- a/game/ui.odin
+++ b/game/ui.odin
@@ -33,7 +33,7 @@ ui_prepare_frame :: proc(world: ^World, dt: f32) {
 	clay.UpdateScrollContainers(false, {}, dt)
 
 	clay.BeginLayout()
-	build_hud(world)
+	build_overlay(world)
 	ui_render_commands = clay.EndLayout(dt)
 }