diff --git a/src/browser/tests/animation/animation.html b/src/browser/tests/animation/animation.html
index 27e562a0..97bfe077 100644
--- a/src/browser/tests/animation/animation.html
+++ b/src/browser/tests/animation/animation.html
@@ -3,13 +3,67 @@
 
 <script id=animation>
   let a1 = document.createElement('div').animate(null, null);
-  testing.expectEqual('finished', a1.playState);
+  testing.expectEqual('idle', a1.playState);
 
   let cb = [];
-  a1.ready.then(() => { cb.push('ready') });
   a1.finished.then((x) => {
-    cb.push('finished');
+    cb.push(a1.playState);
     cb.push(x == a1);
   });
-  testing.eventually(() => testing.expectEqual(['finished', true], cb));
+  a1.ready.then(() => {
+    cb.push(a1.playState);
+    a1.play();
+    cb.push(a1.playState);
+  });
+  testing.eventually(() => testing.expectEqual(['idle', 'running', 'finished', true], cb));
+</script>
+
+<script id=startTime>
+  let a2 = document.createElement('div').animate(null, null);
+  // startTime defaults to null
+  testing.expectEqual(null, a2.startTime);
+  // startTime is settable
+  a2.startTime = 42.5;
+  testing.expectEqual(42.5, a2.startTime);
+  // startTime can be reset to null
+  a2.startTime = null;
+  testing.expectEqual(null, a2.startTime);
+</script>
+
+<script id=onfinish>
+  let a3 = document.createElement('div').animate(null, null);
+  // onfinish defaults to null
+  testing.expectEqual(null, a3.onfinish);
+
+  let calls = [];
+  // onfinish callback should be scheduled and called asynchronously
+  a3.onfinish = function() { calls.push('finish'); };
+  a3.play();
+  testing.eventually(() => testing.expectEqual(['finish'], calls));
+</script>
+
+<script id=pause>
+  let a4 = document.createElement('div').animate(null, null);
+  let cb4 = [];
+  a4.finished.then((x) => { cb4.push(a4.playState) });
+  a4.ready.then(() => {
+    a4.play();
+    cb4.push(a4.playState)
+    a4.pause();
+    cb4.push(a4.playState)
+  });
+  testing.eventually(() => testing.expectEqual(['running', 'paused'], cb4));
+</script>
+
+<script id=finish>
+  let a5 = document.createElement('div').animate(null, null);
+  testing.expectEqual('idle', a5.playState);
+
+  let cb5 = [];
+  a5.finished.then((x) => { cb5.push(a5.playState) });
+  a5.ready.then(() => {
+    cb5.push(a5.playState);
+    a5.play();
+  });
+  testing.eventually(() => testing.expectEqual(['idle', 'finished'], cb5));
 </script>
diff --git a/src/browser/webapi/animation/Animation.zig b/src/browser/webapi/animation/Animation.zig
index 2b6855ac..0ebe396b 100644
--- a/src/browser/webapi/animation/Animation.zig
+++ b/src/browser/webapi/animation/Animation.zig
@@ -16,40 +16,118 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+const std = @import("std");
+const log = @import("../../../log.zig");
 const js = @import("../../js/js.zig");
 const Page = @import("../../Page.zig");
 
+const Allocator = std.mem.Allocator;
+
 const Animation = @This();
 
+const PlayState = enum {
+    idle,
+    running,
+    paused,
+    finished,
+};
+
+_page: *Page,
+_arena: Allocator,
+
 _effect: ?js.Object.Global = null,
 _timeline: ?js.Object.Global = null,
 _ready_resolver: ?js.PromiseResolver.Global = null,
 _finished_resolver: ?js.PromiseResolver.Global = null,
+_startTime: ?f64 = null,
+_onFinish: ?js.Function.Temp = null,
+_playState: PlayState = .idle,
 
+// Fake the animation by passing the states:
+// .idle => .running once play() is called.
+// .running => .finished after 10ms when update() is callback.
+//
+// TODO add support for effect and timeline
 pub fn init(page: *Page) !*Animation {
-    return page._factory.create(Animation{});
+    const arena = try page.getArena(.{ .debug = "Animation" });
+    errdefer page.releaseArena(arena);
+
+    const self = try arena.create(Animation);
+    self.* = .{
+        ._page = page,
+        ._arena = arena,
+    };
+
+    return self;
 }
 
-pub fn play(_: *Animation) void {}
-pub fn pause(_: *Animation) void {}
-pub fn cancel(_: *Animation) void {}
-pub fn finish(_: *Animation) void {}
-pub fn reverse(_: *Animation) void {}
+pub fn deinit(self: *Animation, _: bool) void {
+    self._page.releaseArena(self._arena);
+}
+
+pub fn play(self: *Animation, page: *Page) !void {
+    if (self._playState == .running) {
+        return;
+    }
+
+    // transition to running.
+    self._playState = .running;
+
+    // Schedule the transition from .running => .finished in 10ms.
+    page.js.strongRef(self);
+    try page.js.scheduler.add(
+        self,
+        Animation.update,
+        10,
+        .{ .name = "animation.update" },
+    );
+}
+
+pub fn pause(self: *Animation) void {
+    self._playState = .paused;
+}
+
+pub fn cancel(_: *Animation) void {
+    log.warn(.not_implemented, "Animation.cancel", .{});
+}
+
+pub fn finish(self: *Animation, page: *Page) void {
+    if (self._playState == .finished) {
+        return;
+    }
+
+    self._playState = .finished;
+
+    // resolve finished
+    if (self._finished_resolver) |resolver| {
+        page.js.local.?.toLocal(resolver).resolve("Animation.getFinished", self);
+    }
+    // call onfinish
+    if (self._onFinish) |func| {
+        page.js.local.?.toLocal(func).call(void, .{}) catch |err| {
+            log.warn(.js, "Animation._onFinish", .{ .err = err });
+        };
+    }
+}
+
+pub fn reverse(_: *Animation) void {
+    log.warn(.not_implemented, "Animation.reverse", .{});
+}
 
 pub fn getFinished(self: *Animation, page: *Page) !js.Promise {
     if (self._finished_resolver == null) {
         const resolver = page.js.local.?.createPromiseResolver();
-        resolver.resolve("Animation.getFinished", self);
         self._finished_resolver = try resolver.persist();
         return resolver.promise();
     }
     return page.js.toLocal(self._finished_resolver).?.promise();
 }
 
+// The ready promise is immediately resolved.
 pub fn getReady(self: *Animation, page: *Page) !js.Promise {
-    // never resolved, because we're always "finished"
     if (self._ready_resolver == null) {
         const resolver = page.js.local.?.createPromiseResolver();
+        resolver.resolve("Animation.getReady", self);
         self._ready_resolver = try resolver.persist();
         return resolver.promise();
     }
@@ -72,6 +150,65 @@ pub fn setTimeline(self: *Animation, timeline: ?js.Object.Global) !void {
     self._timeline = timeline;
 }
 
+pub fn getStartTime(self: *const Animation) ?f64 {
+    return self._startTime;
+}
+
+pub fn setStartTime(self: *Animation, value: ?f64, page: *Page) !void {
+    self._startTime = value;
+
+    // if the startTime is null, don't play the animation.
+    if (value == null) {
+        return;
+    }
+
+    return self.play(page);
+}
+
+pub fn getOnFinish(self: *const Animation) ?js.Function.Temp {
+    return self._onFinish;
+}
+
+// callback function transitionning from a state to another
+fn update(ctx: *anyopaque) !?u32 {
+    const self: *Animation = @ptrCast(@alignCast(ctx));
+
+    switch (self._playState) {
+        .running => {
+            // transition to finished.
+            self._playState = .finished;
+
+            var ls: js.Local.Scope = undefined;
+            self._page.js.localScope(&ls);
+            defer ls.deinit();
+
+            // resolve finished
+            if (self._finished_resolver) |resolver| {
+                ls.toLocal(resolver).resolve("Animation.getFinished", self);
+            }
+            // call onfinish
+            if (self._onFinish) |func| {
+                ls.toLocal(func).call(void, .{}) catch |err| {
+                    log.warn(.js, "Animation._onFinish", .{ .err = err });
+                };
+            }
+        },
+        .idle, .paused, .finished => {},
+    }
+
+    // No future change scheduled, set the object weak for garbage collection.
+    self._page.js.weakRef(self);
+    return null;
+}
+
+pub fn setOnFinish(self: *Animation, cb: ?js.Function.Temp) !void {
+    self._onFinish = cb;
+}
+
+pub fn playState(self: *const Animation) []const u8 {
+    return @tagName(self._playState);
+}
+
 pub const JsApi = struct {
     pub const bridge = js.Bridge(Animation);
 
@@ -79,6 +216,8 @@ pub const JsApi = struct {
         pub const name = "Animation";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(Animation.deinit);
     };
 
     pub const play = bridge.function(Animation.play, .{});
@@ -86,12 +225,14 @@ pub const JsApi = struct {
     pub const cancel = bridge.function(Animation.cancel, .{});
     pub const finish = bridge.function(Animation.finish, .{});
     pub const reverse = bridge.function(Animation.reverse, .{});
-    pub const playState = bridge.property("finished", .{ .template = false });
+    pub const playState = bridge.accessor(Animation.playState, null, .{});
     pub const pending = bridge.property(false, .{ .template = false });
     pub const finished = bridge.accessor(Animation.getFinished, null, .{});
     pub const ready = bridge.accessor(Animation.getReady, null, .{});
     pub const effect = bridge.accessor(Animation.getEffect, Animation.setEffect, .{});
     pub const timeline = bridge.accessor(Animation.getTimeline, Animation.setTimeline, .{});
+    pub const startTime = bridge.accessor(Animation.getStartTime, Animation.setStartTime, .{});
+    pub const onfinish = bridge.accessor(Animation.getOnFinish, Animation.setOnFinish, .{});
 };
 
 const testing = @import("../../../testing.zig");