diff --git a/Makefile b/Makefile
index 93ac37c..b149c0a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,8 @@
-.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all toad check test help
+.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all bake toad 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)"
@@ -10,6 +11,9 @@ help:
 	@echo "  check           Typecheck examples/toad"
 	@echo "  toad            Run the toad example"
 
+bake:
+	./scripts/bake_all.sh
+
 shaders-vulkan:
 	./scripts/shaders_vulkan.sh
 
diff --git a/assets_baked/characters/toad/toad.atlas.png b/assets_baked/characters/toad/toad.atlas.png
index f007cf2..f26d742 100644
Binary files a/assets_baked/characters/toad/toad.atlas.png and b/assets_baked/characters/toad/toad.atlas.png differ
diff --git a/assets_baked/characters/toad/toad.char.json b/assets_baked/characters/toad/toad.char.json
index 754f1f1..44ff0fb 100644
--- a/assets_baked/characters/toad/toad.char.json
+++ b/assets_baked/characters/toad/toad.char.json
@@ -10,7 +10,7 @@
     "clips": {
         "walk": {
             "loop": true,
-            "fps": 10.00000000,
+            "fps": 15.00000000,
             "frames": [
                 {
                     "rect": [
@@ -283,80 +283,16 @@
                         0,
                         0
                     ]
-                },
-                {
-                    "rect": [
-                        807,
-                        654,
-                        268,
-                        326
-                    ],
-                    "source_size": [
-                        268,
-                        326
-                    ],
-                    "trim_offset": [
-                        0,
-                        0
-                    ]
                 }
             ]
         },
         "idle": {
             "loop": true,
-            "fps": 10.00000000,
+            "fps": 15.00000000,
             "frames": [
                 {
                     "rect": [
-                        1883,
-                        0,
-                        213,
-                        319
-                    ],
-                    "source_size": [
-                        213,
-                        319
-                    ],
-                    "trim_offset": [
-                        0,
-                        0
-                    ]
-                },
-                {
-                    "rect": [
-                        1883,
-                        320,
-                        213,
-                        319
-                    ],
-                    "source_size": [
-                        213,
-                        319
-                    ],
-                    "trim_offset": [
-                        0,
-                        0
-                    ]
-                },
-                {
-                    "rect": [
-                        1883,
-                        640,
-                        213,
-                        319
-                    ],
-                    "source_size": [
-                        213,
-                        319
-                    ],
-                    "trim_offset": [
-                        0,
-                        0
-                    ]
-                },
-                {
-                    "rect": [
-                        1076,
+                        807,
                         654,
                         213,
                         319
@@ -372,7 +308,7 @@
                 },
                 {
                     "rect": [
-                        1290,
+                        1021,
                         654,
                         213,
                         319
@@ -388,7 +324,7 @@
                 },
                 {
                     "rect": [
-                        1504,
+                        1235,
                         654,
                         213,
                         319
@@ -404,8 +340,8 @@
                 },
                 {
                     "rect": [
-                        1718,
-                        960,
+                        1449,
+                        654,
                         213,
                         319
                     ],
@@ -420,7 +356,23 @@
                 },
                 {
                     "rect": [
-                        1076,
+                        1663,
+                        654,
+                        213,
+                        319
+                    ],
+                    "source_size": [
+                        213,
+                        319
+                    ],
+                    "trim_offset": [
+                        0,
+                        0
+                    ]
+                },
+                {
+                    "rect": [
+                        807,
                         974,
                         213,
                         319
@@ -436,7 +388,7 @@
                 },
                 {
                     "rect": [
-                        1290,
+                        1021,
                         974,
                         213,
                         319
@@ -452,7 +404,39 @@
                 },
                 {
                     "rect": [
-                        1504,
+                        1235,
+                        974,
+                        213,
+                        319
+                    ],
+                    "source_size": [
+                        213,
+                        319
+                    ],
+                    "trim_offset": [
+                        0,
+                        0
+                    ]
+                },
+                {
+                    "rect": [
+                        1449,
+                        974,
+                        213,
+                        319
+                    ],
+                    "source_size": [
+                        213,
+                        319
+                    ],
+                    "trim_offset": [
+                        0,
+                        0
+                    ]
+                },
+                {
+                    "rect": [
+                        1663,
                         974,
                         213,
                         319
@@ -517,7 +501,7 @@
                 {
                     "rect": [
                         642,
-                        981,
+                        1294,
                         213,
                         319
                     ],
@@ -533,23 +517,7 @@
                 {
                     "rect": [
                         856,
-                        981,
-                        213,
-                        319
-                    ],
-                    "source_size": [
-                        213,
-                        319
-                    ],
-                    "trim_offset": [
-                        0,
-                        0
-                    ]
-                },
-                {
-                    "rect": [
-                        1718,
-                        1280,
+                        1294,
                         213,
                         319
                     ],
@@ -593,6 +561,22 @@
                         0,
                         0
                     ]
+                },
+                {
+                    "rect": [
+                        1498,
+                        1294,
+                        213,
+                        319
+                    ],
+                    "source_size": [
+                        213,
+                        319
+                    ],
+                    "trim_offset": [
+                        0,
+                        0
+                    ]
                 }
             ]
         }
diff --git a/content/characters/toad/Walk/skeleton-Walk_17.png b/content/characters/toad/Walk/skeleton-Walk_17.png
deleted file mode 100644
index ce4eeb8..0000000
Binary files a/content/characters/toad/Walk/skeleton-Walk_17.png and /dev/null differ
diff --git a/content/characters/toad/manifest.json b/content/characters/toad/manifest.json
index 27f26cd..240f575 100644
--- a/content/characters/toad/manifest.json
+++ b/content/characters/toad/manifest.json
@@ -5,12 +5,12 @@
   "clips": {
     "idle": {
       "folder": "Idle",
-      "fps": 10,
+      "fps": 15,
       "loop": true
     },
     "walk": {
       "folder": "Walk",
-      "fps": 10,
+      "fps": 15,
       "loop": true
     }
   }
diff --git a/engine/animation_test.odin b/engine/animation_test.odin
new file mode 100644
index 0000000..5905890
--- /dev/null
+++ b/engine/animation_test.odin
@@ -0,0 +1,232 @@
+package engine
+
+import "core:testing"
+
+make_test_character :: proc(allocator := context.allocator) -> Character_Data {
+	data: Character_Data
+	data.def.clips = make(map[string]Clip_Def, allocator)
+
+	idle_frames := make([]Frame_Def, 3, allocator)
+	idle_frames[0] = {
+		rect = {0, 0, 10, 10},
+	}
+	idle_frames[1] = {
+		rect = {10, 0, 10, 10},
+	}
+	idle_frames[2] = {
+		rect = {20, 0, 10, 10},
+	}
+	data.def.clips["idle"] = Clip_Def {
+		loop   = true,
+		fps    = 10,
+		frames = idle_frames,
+	}
+
+	once_frames := make([]Frame_Def, 3, allocator)
+	once_frames[0] = {
+		rect = {0, 10, 10, 10},
+	}
+	once_frames[1] = {
+		rect = {10, 10, 10, 10},
+	}
+	once_frames[2] = {
+		rect = {20, 10, 10, 10},
+	}
+	data.def.clips["once"] = Clip_Def {
+		loop   = false,
+		fps    = 10,
+		frames = once_frames,
+	}
+
+	hold_frames := make([]Frame_Def, 2, allocator)
+	hold_frames[0] = {
+		rect = {0, 20, 10, 10},
+	}
+	hold_frames[1] = {
+		rect = {10, 20, 10, 10},
+	}
+	data.def.clips["hold"] = Clip_Def {
+		loop   = true,
+		fps    = 0,
+		frames = hold_frames,
+	}
+
+	return data
+}
+
+destroy_test_character :: proc(data: ^Character_Data) {
+	if data == nil do return
+	keys := make([dynamic]string, context.temp_allocator)
+	for key, clip in data.def.clips {
+		delete(clip.frames)
+		append(&keys, key)
+	}
+	for key in keys {
+		delete_key(&data.def.clips, key)
+	}
+	delete(data.def.clips)
+	data^ = {}
+}
+
+@(test)
+character_clip_found_and_missing :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	clip, ok := character_clip(&data, "idle")
+	testing.expect(t, ok)
+	testing.expect_value(t, len(clip.frames), 3)
+	testing.expect(t, clip.loop)
+	testing.expect_value(t, clip.fps, f32(10))
+
+	_, ok = character_clip(&data, "missing")
+	testing.expect(t, !ok)
+
+	data.def.clips["empty"] = Clip_Def {
+		loop   = true,
+		fps    = 10,
+		frames = nil,
+	}
+	_, ok = character_clip(&data, "empty")
+	testing.expect(t, !ok)
+}
+
+@(test)
+set_sprite_clip_switch_and_guards :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	sprite := spawn_sprite(&data, {0, 0}, "idle", 0)
+	testing.expect_value(t, sprite.clip, "idle")
+
+	sprite.frame = 2
+	sprite.time = 0.05
+	set_sprite_clip(&sprite, "once")
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect_value(t, sprite.frame, 0)
+	testing.expect_value(t, sprite.time, f32(0))
+
+	sprite.frame = 1
+	sprite.time = 0.09
+	set_sprite_clip(&sprite, "once")
+	testing.expect_value(t, sprite.frame, 1)
+	testing.expect_value(t, sprite.time, f32(0.09))
+
+	set_sprite_clip(&sprite, "nope")
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect_value(t, sprite.frame, 1)
+	testing.expect_value(t, sprite.time, f32(0.09))
+}
+
+@(test)
+spawn_sprite_valid_and_invalid :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {1, 2}, "idle", 0)
+	testing.expect_value(t, s.clip, "idle")
+	testing.expect_value(t, s.frame, 0)
+	testing.expect_value(t, s.time, f32(0))
+	testing.expect_value(t, s.position, Vec2{1, 2})
+
+	s2 := spawn_sprite(&data, {}, "idle", 2)
+	testing.expect_value(t, s2.clip, "idle")
+	testing.expect_value(t, s2.frame, 2)
+
+	s3 := spawn_sprite(&data, {}, "idle", 99)
+	testing.expect_value(t, s3.frame, 2)
+
+	bad := spawn_sprite(&data, {}, "missing", 0)
+	testing.expect_value(t, bad.clip, "")
+	testing.expect_value(t, bad.frame, 0)
+	testing.expect_value(t, bad.time, f32(0))
+}
+
+@(test)
+update_sprite_advances_one_frame :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {}, "idle", 0)
+	update_sprite(&s, 0.1)
+	testing.expect_value(t, s.frame, 1)
+	testing.expect_value(t, s.time, f32(0))
+}
+
+@(test)
+update_sprite_advances_multiple_frames :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	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)
+}
+
+@(test)
+update_sprite_loops :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {}, "idle", 2)
+	update_sprite(&s, 0.1)
+	testing.expect_value(t, s.frame, 0)
+}
+
+@(test)
+update_sprite_non_loop_holds_last :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {}, "once", 2)
+	s.time = 0.05
+	update_sprite(&s, 0.1)
+	testing.expect_value(t, s.frame, 2)
+	testing.expect_value(t, s.time, f32(0))
+}
+
+@(test)
+update_sprite_fps_zero_holds :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {}, "hold", 0)
+	update_sprite(&s, 1.0)
+	testing.expect_value(t, s.frame, 0)
+}
+
+@(test)
+update_sprite_dt_non_positive_noop :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := spawn_sprite(&data, {}, "idle", 0)
+	update_sprite(&s, 0)
+	update_sprite(&s, -0.1)
+	testing.expect_value(t, s.frame, 0)
+	testing.expect_value(t, s.time, f32(0))
+}
+
+@(test)
+update_sprite_nil_and_missing_clip_safe :: proc(t: ^testing.T) {
+	update_sprite(nil, 0.1)
+
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	s := Sprite {
+		data  = &data,
+		clip  = "missing",
+		frame = 0,
+		time  = 0,
+	}
+	update_sprite(&s, 0.1)
+	testing.expect_value(t, s.frame, 0)
+
+	s2 := Sprite {
+		data = nil,
+		clip = "idle",
+	}
+	update_sprite(&s2, 0.1)
+}
diff --git a/engine/character_data.odin b/engine/character_data.odin
index 6fe670e..03504fe 100644
--- a/engine/character_data.odin
+++ b/engine/character_data.odin
@@ -170,7 +170,10 @@ load_character_data :: proc(app: ^App, character_json_path: string) -> (Characte
 	sdl.EndGPUCopyPass(copy_pass)
 	fence := sdl.SubmitGPUCommandBufferAndAcquireFence(cmd)
 	if fence == nil {
-		fmt.eprintfln("SubmitGPUCommandBufferAndAcquireFence (texture upload) failed: %s", sdl.GetError())
+		fmt.eprintfln(
+			"SubmitGPUCommandBufferAndAcquireFence (texture upload) failed: %s",
+			sdl.GetError(),
+		)
 		sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
 		sdl.ReleaseGPUTexture(app.device, out.texture)
 		return {}, false
@@ -200,6 +203,13 @@ destroy_character_data :: proc(app: ^App, data: ^Character_Data) {
 	data^ = {}
 }
 
+character_clip :: proc(data: ^Character_Data, clip_name: string) -> (clip: Clip_Def, ok: bool) {
+	if data == nil do return {}, false
+	character, found := data.def.clips[clip_name]
+	if !found || len(character.frames) == 0 do return {}, false
+	return character, true
+}
+
 character_frame_rect :: proc(
 	data: ^Character_Data,
 	clip_name: string,
diff --git a/engine/sprite.odin b/engine/sprite.odin
index 22c11f2..fb46604 100644
--- a/engine/sprite.odin
+++ b/engine/sprite.odin
@@ -10,6 +10,7 @@ Sprite :: struct {
 	position: Vec2,
 	clip:     string,
 	frame:    int,
+	time:     f32,
 }
 
 spawn_sprite :: proc(
@@ -18,13 +19,61 @@ spawn_sprite :: proc(
 	clip: string = "idle",
 	frame: int = 0,
 ) -> Sprite {
-	return Sprite{data = data, position = position, clip = clip, frame = frame}
+	sprite := Sprite {
+		data     = data,
+		position = position,
+	}
+	set_sprite_clip(&sprite, clip)
+	if frame != 0 {
+		c, ok := character_clip(sprite.data, sprite.clip)
+		if ok {
+			if frame < 0 {
+				sprite.frame = 0
+			} else if frame >= len(c.frames) {
+				sprite.frame = len(c.frames) - 1
+			} else {
+				sprite.frame = frame
+			}
+		}
+	}
+	return sprite
 }
 
 // stubbed for later
 update_sprite :: proc(sprite: ^Sprite, dt: f32) {
-	_ = sprite
-	_ = dt
+	if sprite == nil || sprite.data == nil do return
+	if dt <= 0 do return
+
+	clip, ok := character_clip(sprite.data, sprite.clip)
+	if !ok do return
+
+	frame_count := len(clip.frames)
+	if frame_count <= 0 do return
+
+	if sprite.frame < 0 do sprite.frame = 0
+	if sprite.frame >= frame_count do sprite.frame = frame_count - 1
+
+	if clip.fps <= 0 do return
+
+	sprite.time += dt
+	frame_duration := 1.0 / clip.fps
+
+	for sprite.time >= frame_duration {
+		sprite.time -= frame_duration
+		next := sprite.frame + 1
+
+		if next >= frame_count {
+			if clip.loop {
+				sprite.frame = 0
+			} else {
+				sprite.frame = frame_count - 1
+				sprite.time = 0
+				break
+			}
+		} else {
+			sprite.frame = next
+		}
+	}
 }
 
 to_clip :: proc(px, py, sw, sh: f32) -> [2]f32 {
@@ -129,3 +178,16 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 
 	sdl.DrawGPUPrimitives(app.render_pass, 6, 1, 0, 0)
 }
+
+set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {
+	if sprite == nil || sprite.data == nil do return
+
+	if sprite.clip == clip do return
+
+	_, ok := character_clip(sprite.data, clip)
+	if !ok do return
+
+	sprite.clip = clip
+	sprite.frame = 0
+	sprite.time = 0
+}
diff --git a/engine/time.odin b/engine/time.odin
new file mode 100644
index 0000000..01273ac
--- /dev/null
+++ b/engine/time.odin
@@ -0,0 +1,8 @@
+package engine
+
+import sdl "vendor:sdl3"
+
+// now_seconds returns seconds since SDL init (monotonic for frame timing).
+now_seconds :: proc() -> f64 {
+	return f64(sdl.GetTicksNS()) / 1_000_000_000.0
+}
diff --git a/examples/toad/main.odin b/examples/toad/main.odin
index ad21f35..45fce0d 100644
--- a/examples/toad/main.odin
+++ b/examples/toad/main.odin
@@ -4,7 +4,7 @@ import eng "pkg:engine"
 
 main :: proc() {
 	app: eng.App
-	if !eng.init(&app, "toad", 800, 600) do return
+	if !eng.init(&app, "toad game", 800, 600) do return
 	defer eng.shutdown(&app)
 
 	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
@@ -14,10 +14,17 @@ main :: proc() {
 
 	toad := eng.spawn_sprite(&data, {400, 500}, "idle", 0)
 
+	last := eng.now_seconds()
+
 	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+
+		eng.update_sprite(&toad, dt)
+
 		eng.begin_frame(&app)
 		eng.draw_sprite(&app, &toad)
 		eng.end_frame(&app)
 	}
 }
-
diff --git a/scripts/bake_all.sh b/scripts/bake_all.sh
new file mode 100755
index 0000000..9b845f8
--- /dev/null
+++ b/scripts/bake_all.sh
@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$ROOT"
+
+CONTENT_ROOT="${CONTENT_ROOT:-content/characters}"
+OUT_ROOT="${OUT_ROOT:-assets_baked/characters}"
+
+if [[ ! -d "$CONTENT_ROOT" ]]; then
+	echo "missing content root: $CONTENT_ROOT" >&2
+	exit 1
+fi
+
+shopt -s nullglob
+manifests=("$CONTENT_ROOT"/*/manifest.json)
+if [[ ${#manifests[@]} -eq 0 ]]; then
+	echo "no character manifests under $CONTENT_ROOT" >&2
+	exit 1
+fi
+
+for manifest in "${manifests[@]}"; do
+	char_dir="$(dirname "$manifest")"
+	name="$(basename "$char_dir")"
+	out_dir="$OUT_ROOT/$name"
+	mkdir -p "$out_dir"
+	echo "baking $name -> $out_dir"
+	odin run assetbake -- "$char_dir" "$out_dir"
+done
+
+echo "baked ${#manifests[@]} character(s)"