Add missing changes that causes failures

Batch adjacent same-texture sprite draws in end_frame.
Replaces per-sprite DrawGPUPrimitives with texture runs so shared atlases issue one GPU draw.

Makefile

@@ -1,15 +1,19 @@
-.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all bake toad check test help
+.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all bake toad hello_sprite crowd camera_sandbox clips check test help
 
 help:
 	@echo "Targets:"
-	@echo "  bake            Bake all characters under content/characters/"
-	@echo "  shaders-vulkan  Compile SPIR-V into shaders/vulkan/"
-	@echo "  shaders-d3d12   Compile DXIL into shaders/d3d12/ (needs shadercross)"
-	@echo "  shaders-metal   Compile MSL into shaders/metal/ (needs shadercross)"
-	@echo "  shaders-all     Build all shader backends"
-	@echo "  test            Run engine unit tests"
-	@echo "  check           Typecheck examples/toad"
-	@echo "  toad            Run the toad example"
+	@echo "  bake             Bake all characters under content/characters/"
+	@echo "  shaders-vulkan   Compile SPIR-V into shaders/vulkan/"
+	@echo "  shaders-d3d12    Compile DXIL into shaders/d3d12/ (needs shadercross)"
+	@echo "  shaders-metal    Compile MSL into shaders/metal/ (needs shadercross)"
+	@echo "  shaders-all      Build all shader backends"
+	@echo "  test             Run engine unit tests"
+	@echo "  check            Typecheck all examples"
+	@echo "  toad             Run the toad example (full demo)"
+	@echo "  hello_sprite     Minimal load + draw"
+	@echo "  crowd            Many sprites, one Character_Data"
+	@echo "  camera_sandbox   Pan camera / Space toggles follow"
+	@echo "  clips            Keys 1/2 switch idle/walk"
 
 bake:
 	./scripts/bake_all.sh
@@ -30,6 +34,22 @@ test:
 
 check:
 	odin check examples/toad -collection:pkg=.
+	odin check examples/hello_sprite -collection:pkg=.
+	odin check examples/crowd -collection:pkg=.
+	odin check examples/camera_sandbox -collection:pkg=.
+	odin check examples/clips -collection:pkg=.
 
 toad:
 	odin run examples/toad -collection:pkg=.
+
+hello_sprite:
+	odin run examples/hello_sprite -collection:pkg=.
+
+crowd:
+	odin run examples/crowd -collection:pkg=.
+
+camera_sandbox:
+	odin run examples/camera_sandbox -collection:pkg=.
+
+clips:
+	odin run examples/clips -collection:pkg=.

assetbake/main.odin

@@ -287,16 +287,14 @@ destroy_frames :: proc(frames: []^image.Image) {
 	delete(frames)
 }
 
-opaque_bounds :: proc(img: ^image.Image, alpha_min: u8 = 1) -> (x, y, w, h: int) {
-	iw, ih := int(img.width), int(img.height)
-	pixels := bytes.buffer_to_bytes(&img.pixels)
-
+opaque_bounds_rgba :: proc(pixels: []u8, iw, ih: int, alpha_min: u8 = 1) -> (x, y, w, h: int) {
 	min_x, min_y := iw, ih
 	max_x, max_y := -1, -1
 
 	for py in 0 ..< ih {
 		for px in 0 ..< iw {
 			i := (py * iw + px) * 4
+			if i + 3 >= len(pixels) do continue
 			a := pixels[i + 3]
 			if a >= alpha_min {
 				if px < min_x do min_x = px
@@ -313,6 +311,12 @@ opaque_bounds :: proc(img: ^image.Image, alpha_min: u8 = 1) -> (x, y, w, h: int)
 	return min_x, min_y, max_x - min_x + 1, max_y - min_y + 1
 }
 
+opaque_bounds :: proc(img: ^image.Image, alpha_min: u8 = 1) -> (x, y, w, h: int) {
+	iw, ih := int(img.width), int(img.height)
+	pixels := bytes.buffer_to_bytes(&img.pixels)
+	return opaque_bounds_rgba(pixels, iw, ih, alpha_min)
+}
+
 pack_atlas :: proc(frames: []^image.Image) -> Atlas {
 	PADDING :: 1
 

assetbake/opaque_bounds_test.odin

@@ -0,0 +1,46 @@
+package main
+
+import "core:testing"
+
+@(test)
+opaque_bounds_inset :: proc(t: ^testing.T) {
+	// 4x4, opaque 2x2 at (1,1)
+	pixels := make([]u8, 4 * 4 * 4)
+	defer delete(pixels)
+	for y in 1 ..= 2 {
+		for x in 1 ..= 2 {
+			i := (y * 4 + x) * 4
+			pixels[i + 3] = 255
+		}
+	}
+	x, y, w, h := opaque_bounds_rgba(pixels, 4, 4)
+	testing.expect_value(t, x, 1)
+	testing.expect_value(t, y, 1)
+	testing.expect_value(t, w, 2)
+	testing.expect_value(t, h, 2)
+}
+
+@(test)
+opaque_bounds_full :: proc(t: ^testing.T) {
+	pixels := make([]u8, 2 * 2 * 4)
+	defer delete(pixels)
+	for i := 3; i < len(pixels); i += 4 {
+		pixels[i] = 255
+	}
+	x, y, w, h := opaque_bounds_rgba(pixels, 2, 2)
+	testing.expect_value(t, x, 0)
+	testing.expect_value(t, y, 0)
+	testing.expect_value(t, w, 2)
+	testing.expect_value(t, h, 2)
+}
+
+@(test)
+opaque_bounds_empty :: proc(t: ^testing.T) {
+	pixels := make([]u8, 3 * 3 * 4)
+	defer delete(pixels)
+	x, y, w, h := opaque_bounds_rgba(pixels, 3, 3)
+	testing.expect_value(t, x, 0)
+	testing.expect_value(t, y, 0)
+	testing.expect_value(t, w, 1)
+	testing.expect_value(t, h, 1)
+}

engine/animation_test.odin

@@ -74,13 +74,13 @@ character_clip_found_and_missing :: proc(t: ^testing.T) {
 	defer destroy_test_character(&data)
 
 	clip, ok := character_clip(&data, "idle")
-	testing.expect(t, ok)
+	testing.expect(t, ok, "character_clip should find idle")
 	testing.expect_value(t, len(clip.frames), 3)
-	testing.expect(t, clip.loop)
+	testing.expect(t, clip.loop, "idle clip should loop")
 	testing.expect_value(t, clip.fps, f32(10))
 
 	_, ok = character_clip(&data, "missing")
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "character_clip should miss unknown name")
 
 	data.def.clips["empty"] = Clip_Def {
 		loop   = true,
@@ -88,7 +88,7 @@ character_clip_found_and_missing :: proc(t: ^testing.T) {
 		frames = nil,
 	}
 	_, ok = character_clip(&data, "empty")
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "character_clip should reject empty frames")
 }
 
 @(test)
@@ -161,7 +161,7 @@ update_sprite_advances_multiple_frames :: proc(t: ^testing.T) {
 	s := spawn_sprite(&data, {}, "idle", 0)
 	update_sprite(&s, 0.25)
 	testing.expect_value(t, s.frame, 2)
-	testing.expect(t, s.time > 0.049 && s.time < 0.051)
+	testing.expect(t, s.time > 0.049 && s.time < 0.051, "leftover time after multi-frame advance should be ~0.05")
 }
 
 @(test)

engine/app.odin

@@ -35,6 +35,7 @@ App :: struct {
 	transfer_buffer:   ^sdl.GPUTransferBuffer,
 	draw_list:         [dynamic]Queued_Sprite,
 	clear_color:       sdl.FColor,
+	camera:            Camera,
 }
 
 Shader_Backend :: enum {
@@ -124,6 +125,8 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 
 	app.draw_list = make([dynamic]Queued_Sprite)
 
+	app.camera = camera_default()
+
 	return true
 }
 

engine/batching_test.odin

@@ -0,0 +1,64 @@
+package engine
+
+import "core:testing"
+import sdl "vendor:sdl3"
+
+fake_tex :: proc(id: uintptr) -> ^sdl.GPUTexture {
+	return cast(^sdl.GPUTexture)id
+}
+
+@(test)
+texture_run_len_empty_or_oob :: proc(t: ^testing.T) {
+	testing.expect_value(t, texture_run_len(nil, 0), 0)
+	list := []Queued_Sprite{}
+	testing.expect_value(t, texture_run_len(list, 0), 0)
+	list = make([]Queued_Sprite, 1)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	testing.expect_value(t, texture_run_len(list, -1), 0)
+	testing.expect_value(t, texture_run_len(list, 1), 0)
+}
+
+@(test)
+texture_run_len_single :: proc(t: ^testing.T) {
+	list := make([]Queued_Sprite, 1)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	testing.expect_value(t, texture_run_len(list, 0), 1)
+}
+
+@(test)
+texture_run_len_same_texture :: proc(t: ^testing.T) {
+	tex := fake_tex(1)
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = tex}
+	list[1] = {texture = tex}
+	list[2] = {texture = tex}
+	testing.expect_value(t, texture_run_len(list, 0), 3)
+}
+
+@(test)
+texture_run_len_breaks_on_change :: proc(t: ^testing.T) {
+	a := fake_tex(1)
+	b := fake_tex(2)
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = a}
+	list[1] = {texture = a}
+	list[2] = {texture = b}
+	testing.expect_value(t, texture_run_len(list, 0), 2)
+	testing.expect_value(t, texture_run_len(list, 2), 1)
+}
+
+@(test)
+texture_run_len_all_different :: proc(t: ^testing.T) {
+	list := make([]Queued_Sprite, 3)
+	defer delete(list)
+	list[0] = {texture = fake_tex(1)}
+	list[1] = {texture = fake_tex(2)}
+	list[2] = {texture = fake_tex(3)}
+	testing.expect_value(t, texture_run_len(list, 0), 1)
+	testing.expect_value(t, texture_run_len(list, 1), 1)
+	testing.expect_value(t, texture_run_len(list, 2), 1)
+}

engine/camera.odin

@@ -0,0 +1,17 @@
+package engine
+
+Camera :: struct {
+	position: Vec2,
+	anchor:   Vec2,
+}
+
+camera_default :: proc() -> Camera {
+	return Camera{position = {0, 0}, anchor = {0.5, 0.5}}
+}
+
+world_to_screen :: proc(cam: Camera, world: Vec2, viewport: Vec2) -> Vec2 {
+	return {
+		world.x - cam.position.x + viewport.x * cam.anchor[0],
+		world.y - cam.position.y + viewport.y * cam.anchor[1],
+	}
+}

engine/camera_test.odin

@@ -0,0 +1,44 @@
+package engine
+
+import "core:testing"
+
+@(test)
+camera_default_values :: proc(t: ^testing.T) {
+	cam := camera_default()
+	testing.expect_value(t, cam.position, Vec2{0, 0})
+	testing.expect_value(t, cam.anchor, Vec2{0.5, 0.5})
+}
+
+@(test)
+world_to_screen_centered_identity :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {400, 500},
+		anchor   = {0.5, 0.5},
+	}
+	viewport := Vec2{800, 600}
+	screen := world_to_screen(cam, cam.position, viewport)
+	testing.expect_value(t, screen.x, f32(400))
+	testing.expect_value(t, screen.y, f32(300))
+}
+
+@(test)
+world_to_screen_origin_cam :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {0, 0},
+		anchor   = {0.5, 0.5},
+	}
+	screen := world_to_screen(cam, {10, 20}, {200, 100})
+	testing.expect_value(t, screen.x, f32(110))
+	testing.expect_value(t, screen.y, f32(70))
+}
+
+@(test)
+world_to_screen_top_left_anchor :: proc(t: ^testing.T) {
+	cam := Camera {
+		position = {5, 7},
+		anchor   = {0, 0},
+	}
+	screen := world_to_screen(cam, {15, 27}, {800, 600})
+	testing.expect_value(t, screen.x, f32(10))
+	testing.expect_value(t, screen.y, f32(20))
+}

engine/character_data_test.odin

@@ -11,7 +11,7 @@ parse_char_def_happy_path :: proc(t: ^testing.T) {
 	def, ok := parse_char_def(src)
 	defer destroy_char_def(&def)
 
-	testing.expect(t, ok)
+	testing.expect(t, ok, "parse_char_def should succeed on valid JSON")
 	testing.expect_value(t, def.id, "toad")
 	testing.expect_value(t, def.atlas, "toad.atlas.png")
 	testing.expect_value(t, def.version, 1)
@@ -20,8 +20,8 @@ parse_char_def_happy_path :: proc(t: ^testing.T) {
 	testing.expect_value(t, def.pivot[1], f32(1.0))
 
 	idle, found := def.clips["idle"]
-	testing.expect(t, found)
-	testing.expect(t, idle.loop)
+	testing.expect(t, found, "expected idle clip in parsed def")
+	testing.expect(t, idle.loop, "idle clip should loop")
 	testing.expect_value(t, idle.fps, f32(8.0))
 	testing.expect_value(t, len(idle.frames), 1)
 	testing.expect_value(t, idle.frames[0].rect, [4]int{1, 2, 3, 4})
@@ -30,7 +30,7 @@ parse_char_def_happy_path :: proc(t: ^testing.T) {
 @(test)
 parse_char_def_bad_json :: proc(t: ^testing.T) {
 	_, ok := parse_char_def(transmute([]u8)string("{ not json"))
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "parse_char_def should fail on invalid JSON")
 }
 
 @(test)
@@ -51,17 +51,66 @@ character_frame_rect_hit_and_miss :: proc(t: ^testing.T) {
 	}
 
 	rect, ok := character_frame_rect(&data, "idle", 1)
-	testing.expect(t, ok)
+	testing.expect(t, ok, "character_frame_rect should find idle frame 1")
 	testing.expect_value(t, rect, [4]int{50, 60, 70, 80})
 
 	_, ok = character_frame_rect(&data, "missing", 0)
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "character_frame_rect should miss unknown clip")
 
 	_, ok = character_frame_rect(&data, "idle", -1)
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "character_frame_rect should reject negative index")
 
 	_, ok = character_frame_rect(&data, "idle", 2)
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "character_frame_rect should reject out-of-range index")
+}
+
+@(test)
+character_frame_returns_full_def :: proc(t: ^testing.T) {
+	data: Character_Data
+	data.def.clips = make(map[string]Clip_Def)
+	defer delete(data.def.clips)
+
+	frames := make([]Frame_Def, 1)
+	frames[0] = Frame_Def {
+		rect        = {10, 20, 30, 40},
+		source_size = {100, 200},
+		trim_offset = {5, 7},
+	}
+	defer delete(frames)
+
+	data.def.clips["idle"] = Clip_Def {
+		loop   = true,
+		fps    = 10,
+		frames = frames,
+	}
+
+	frame, ok := character_frame(&data, "idle", 0)
+	testing.expect(t, ok, "character_frame should find idle frame 0")
+	testing.expect_value(t, frame.rect, [4]int{10, 20, 30, 40})
+	testing.expect_value(t, frame.source_size, [2]int{100, 200})
+	testing.expect_value(t, frame.trim_offset, [2]int{5, 7})
+}
+
+@(test)
+character_frame_nil_and_bad_index :: proc(t: ^testing.T) {
+	_, ok := character_frame(nil, "idle", 0)
+	testing.expect(t, !ok, "character_frame should fail on nil data")
+
+	data: Character_Data
+	data.def.clips = make(map[string]Clip_Def)
+	defer delete(data.def.clips)
+
+	frames := make([]Frame_Def, 1)
+	frames[0] = {rect = {1, 2, 3, 4}}
+	defer delete(frames)
+	data.def.clips["idle"] = Clip_Def{frames = frames}
+
+	_, ok = character_frame(&data, "idle", -1)
+	testing.expect(t, !ok, "character_frame should reject negative index")
+	_, ok = character_frame(&data, "idle", 1)
+	testing.expect(t, !ok, "character_frame should reject out-of-range index")
+	_, ok = character_frame(&data, "missing", 0)
+	testing.expect(t, !ok, "character_frame should miss unknown clip")
 }
 
 destroy_char_def :: proc(def: ^Char_Def) {

engine/input.odin

@@ -7,6 +7,11 @@ Key :: enum {
 	D,
 	Left,
 	Right,
+	Up,
+	Down,
+	Space,
+	N1,
+	N2,
 }
 
 key_down :: proc(key: Key) -> bool {
@@ -23,6 +28,16 @@ key_down :: proc(key: Key) -> bool {
 		scan_code = .LEFT
 	case .Right:
 		scan_code = .RIGHT
+	case .Up:
+		scan_code = .UP
+	case .Down:
+		scan_code = .DOWN
+	case .Space:
+		scan_code = .SPACE
+	case .N1:
+		scan_code = ._1
+	case .N2:
+		scan_code = ._2
 	}
 	return keys[scan_code]
 }

engine/shader_backend_test.odin

@@ -21,7 +21,7 @@ shader_filenames_per_backend :: proc(t: ^testing.T) {
 @(test)
 choose_shader_runtime_prefers_msl :: proc(t: ^testing.T) {
 	rt, ok := choose_shader_runtime_from_formats({.MSL, .SPIRV, .DXIL})
-	testing.expect(t, ok)
+	testing.expect(t, ok, "should pick a runtime when MSL is available")
 	testing.expect_value(t, rt.backend, Shader_Backend.Metal_MSL)
 	testing.expect_value(t, rt.shader_dir, "shaders/metal")
 	testing.expect_value(t, rt.format, sdl.GPUShaderFormat{.MSL})
@@ -30,7 +30,7 @@ choose_shader_runtime_prefers_msl :: proc(t: ^testing.T) {
 @(test)
 choose_shader_runtime_spirv_only :: proc(t: ^testing.T) {
 	rt, ok := choose_shader_runtime_from_formats({.SPIRV})
-	testing.expect(t, ok)
+	testing.expect(t, ok, "should pick SPIR-V when it is the only format")
 	testing.expect_value(t, rt.backend, Shader_Backend.Vulkan_SPIRV)
 	testing.expect_value(t, rt.shader_dir, "shaders/vulkan")
 	testing.expect_value(t, rt.format, sdl.GPUShaderFormat{.SPIRV})
@@ -39,5 +39,5 @@ choose_shader_runtime_spirv_only :: proc(t: ^testing.T) {
 @(test)
 choose_shader_runtime_empty_fails :: proc(t: ^testing.T) {
 	_, ok := choose_shader_runtime_from_formats({})
-	testing.expect(t, !ok)
+	testing.expect(t, !ok, "empty format set should fail")
 }

engine/sprite.odin

@@ -109,19 +109,18 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 	trim_y := f32(frame.trim_offset[1])
 	pivot := sprite.data.def.pivot
 
-	canvas_top := sprite.position.y - src_h * pivot[1]
-	x0_px, y0_px: f32
-	if sprite.flip_x {
-		canvas_left := sprite.position.x - (1.0 - pivot[0]) * src_w
-		x0_px = canvas_left + (src_w - trim_x - fw)
-		y0_px = canvas_top + trim_y
-	} else {
-		canvas_left := sprite.position.x - src_w * pivot[0]
-		x0_px = canvas_left + trim_x
-		y0_px = canvas_top + trim_y
-	}
-	x1_px := x0_px + fw
-	y1_px := y0_px + fh
+	viewport := Vec2{f32(app.swapchain_w), f32(app.swapchain_h)}
+	feet := world_to_screen(app.camera, sprite.position, viewport)
+
+	x0_px, y0_px, x1_px, y1_px := sprite_feet_quad(
+		feet,
+		src_w,
+		src_h,
+		{trim_x, trim_y},
+		{fw, fh},
+		pivot,
+		sprite.flip_x,
+	)
 
 	sw := f32(app.swapchain_w)
 	sh := f32(app.swapchain_h)
@@ -132,11 +131,7 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 
 	tex_w := f32(sprite.data.width)
 	tex_h := f32(sprite.data.height)
-	u0 := f32(frame.rect[0]) / tex_w
-	v0 := f32(frame.rect[1]) / tex_h
-	u1 := f32(frame.rect[0] + frame.rect[2]) / tex_w
-	v1 := f32(frame.rect[1] + frame.rect[3]) / tex_h
-	if sprite.flip_x do u0, u1 = u1, u0
+	u0, v0, u1, v1 := frame_uvs(frame.rect, tex_w, tex_h, sprite.flip_x)
 
 	verts := [SPRITE_VERT_COUNT]Vertex {
 		{pos = p0, uv = {u0, v0}},
@@ -147,10 +142,7 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 		{pos = p3, uv = {u0, v1}},
 	}
 
-	append(
-		&app.draw_list,
-		Queued_Sprite{texture = sprite.data.texture, verts = verts},
-	)
+	append(&app.draw_list, Queued_Sprite{texture = sprite.data.texture, verts = verts})
 }
 
 set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {
@@ -170,6 +162,40 @@ sprite_quad_origin :: proc(position: Vec2, size: Vec2, pivot: [2]f32) -> Vec2 {
 	return {position.x - size.x * pivot[0], position.y - size.y * pivot[1]}
 }
 
+frame_uvs :: proc(rect: [4]int, tex_w, tex_h: f32, flip_x: bool) -> (u0, v0, u1, v1: f32) {
+	u0 = f32(rect[0]) / tex_w
+	v0 = f32(rect[1]) / tex_h
+	u1 = f32(rect[0] + rect[2]) / tex_w
+	v1 = f32(rect[1] + rect[3]) / tex_h
+	if flip_x do u0, u1 = u1, u0
+	return
+}
+
+sprite_feet_quad :: proc(
+	feet: Vec2,
+	src_w, src_h: f32,
+	trim: Vec2,
+	size: Vec2,
+	pivot: [2]f32,
+	flip_x: bool,
+) -> (
+	x0, y0, x1, y1: f32,
+) {
+	canvas_top := feet.y - src_h * pivot[1]
+	if flip_x {
+		canvas_left := feet.x - (1.0 - pivot[0]) * src_w
+		x0 = canvas_left + (src_w - trim.x - size.x)
+		y0 = canvas_top + trim.y
+	} else {
+		canvas_left := feet.x - src_w * pivot[0]
+		x0 = canvas_left + trim.x
+		y0 = canvas_top + trim.y
+	}
+	x1 = x0 + size.x
+	y1 = y0 + size.y
+	return
+}
+
 set_sprite_flip_x :: proc(sprite: ^Sprite, flip: bool) {
 	if sprite == nil do return
 	sprite.flip_x = flip

engine/sprite_test.odin

@@ -33,3 +33,59 @@ sprite_quad_origin_center :: proc(t: ^testing.T) {
 	testing.expect_value(t, o.x, f32(350))
 	testing.expect_value(t, o.y, f32(400))
 }
+
+@(test)
+frame_uvs_unflipped :: proc(t: ^testing.T) {
+	u0, v0, u1, v1 := frame_uvs({10, 20, 30, 40}, 100, 200, false)
+	testing.expect_value(t, u0, f32(0.1))
+	testing.expect_value(t, v0, f32(0.1))
+	testing.expect_value(t, u1, f32(0.4))
+	testing.expect_value(t, v1, f32(0.3))
+	testing.expect(t, u0 < u1, "unflipped UVs should have u0 < u1")
+}
+
+@(test)
+frame_uvs_flipped :: proc(t: ^testing.T) {
+	a0, _, a1, _ := frame_uvs({10, 20, 30, 40}, 100, 200, false)
+	b0, v0, b1, v1 := frame_uvs({10, 20, 30, 40}, 100, 200, true)
+	testing.expect_value(t, b0, a1)
+	testing.expect_value(t, b1, a0)
+	testing.expect_value(t, v0, f32(0.1))
+	testing.expect_value(t, v1, f32(0.3))
+}
+
+@(test)
+sprite_feet_quad_no_flip :: proc(t: ^testing.T) {
+	// feet (400,500), source 100x200, pivot feet, trim (10,20), packed 80x160
+	x0, y0, x1, y1 := sprite_feet_quad(
+		{400, 500},
+		100,
+		200,
+		{10, 20},
+		{80, 160},
+		{0.5, 1.0},
+		false,
+	)
+	testing.expect_value(t, x0, f32(360)) // 400 - 50 + 10
+	testing.expect_value(t, y0, f32(320)) // 500 - 200 + 20
+	testing.expect_value(t, x1, f32(440))
+	testing.expect_value(t, y1, f32(480))
+}
+
+@(test)
+sprite_feet_quad_flip_x :: proc(t: ^testing.T) {
+	x0, y0, x1, y1 := sprite_feet_quad(
+		{400, 500},
+		100,
+		200,
+		{5, 20},
+		{80, 160},
+		{0.5, 1.0},
+		true,
+	)
+	// canvas_left = 350; trim_x_draw = 100 - 5 - 80 = 15 → x0 = 365
+	testing.expect_value(t, x0, f32(365))
+	testing.expect_value(t, y0, f32(320))
+	testing.expect_value(t, x1, f32(445))
+	testing.expect_value(t, y1, f32(480))
+}

examples/camera_sandbox/main.odin

@@ -0,0 +1,58 @@
+package main
+
+import eng "pkg:engine"
+
+// Camera sandbox: toad stays put; arrows pan the camera. Space toggles follow mode.
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "camera sandbox", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	toad := eng.spawn_sprite(&data, {0, 0}, "idle", 0)
+	app.camera.position = {0, -100}
+
+	follow := false
+	space_was_down := false
+	CAM_SPEED :: f32(300)
+
+	last := eng.now_seconds()
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+
+		space := eng.key_down(.Space)
+		if space && !space_was_down {
+			follow = !follow
+		}
+		space_was_down = space
+
+		if follow {
+			app.camera.position = toad.position - {0, 100}
+		} else {
+			if eng.key_down(.Left) || eng.key_down(.A) {
+				app.camera.position.x -= CAM_SPEED * dt
+			}
+			if eng.key_down(.Right) || eng.key_down(.D) {
+				app.camera.position.x += CAM_SPEED * dt
+			}
+			if eng.key_down(.Up) {
+				app.camera.position.y -= CAM_SPEED * dt
+			}
+			if eng.key_down(.Down) {
+				app.camera.position.y += CAM_SPEED * dt
+			}
+		}
+
+		eng.update_sprite(&toad, dt)
+
+		eng.begin_frame(&app)
+		eng.draw_sprite(&app, &toad)
+		eng.end_frame(&app)
+	}
+}

examples/clips/main.odin

@@ -0,0 +1,38 @@
+package main
+
+import eng "pkg:engine"
+
+// Clip switcher: 1 = idle, 2 = walk. No movement — animation policy only.
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "clips", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	toad := eng.spawn_sprite(&data, {400, 500}, "idle", 0)
+	app.camera.position = toad.position - {0, 100}
+
+	last := eng.now_seconds()
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+
+		if eng.key_down(.N1) {
+			eng.set_sprite_clip(&toad, "idle")
+		}
+		if eng.key_down(.N2) {
+			eng.set_sprite_clip(&toad, "walk")
+		}
+
+		eng.update_sprite(&toad, dt)
+
+		eng.begin_frame(&app)
+		eng.draw_sprite(&app, &toad)
+		eng.end_frame(&app)
+	}
+}

examples/crowd/main.odin

@@ -0,0 +1,49 @@
+package main
+
+import eng "pkg:engine"
+
+// Many sprites sharing one Character_Data (Flyweight) — good batching demo.
+COUNT :: 24
+
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "crowd", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	sprites: [COUNT]eng.Sprite
+	for i in 0 ..< COUNT {
+		col := i % 8
+		row := i / 8
+		pos := eng.Vec2 {
+			f32(120 + col * 80),
+			f32(280 + row * 120),
+		}
+		clip := "idle" if (i % 2) == 0 else "walk"
+		sprites[i] = eng.spawn_sprite(&data, pos, clip, i % 5)
+	}
+
+	// Look at the middle of the grid
+	app.camera.position = {400, 400}
+
+	last := eng.now_seconds()
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+
+		for &s in sprites {
+			eng.update_sprite(&s, dt)
+		}
+
+		eng.begin_frame(&app)
+		for &s in sprites {
+			eng.draw_sprite(&app, &s)
+		}
+		eng.end_frame(&app)
+	}
+}

examples/hello_sprite/main.odin

@@ -0,0 +1,34 @@
+package main
+
+import eng "pkg:engine"
+
+// Minimal: load one baked character and draw idle. No input, no camera follow.
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "hello sprite", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	sprite := eng.spawn_sprite(&data, {400, 500}, "idle", 0)
+
+	// Screen-centered framing without gameplay camera follow:
+	// treat spawn position as world; look slightly above feet.
+	app.camera.position = sprite.position - {0, 100}
+
+	last := eng.now_seconds()
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+
+		eng.update_sprite(&sprite, dt)
+
+		eng.begin_frame(&app)
+		eng.draw_sprite(&app, &sprite)
+		eng.end_frame(&app)
+	}
+}

examples/toad/main.odin

@@ -39,6 +39,8 @@ main :: proc() {
 		} else {
 			eng.set_sprite_clip(&toad, "idle")
 		}
+
+		app.camera.position = toad.position - {0, 100}
 		eng.update_sprite(&toad, dt)
 
 		eng.begin_frame(&app)