diff --git a/.gitignore b/.gitignore
index 380e562b06..a999190ceb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,7 +8,7 @@ node_modules
 /internal.*
 /store.js
 /easing.js
-/motion.js
+/motion.*
 /transition.js
 /scratch/
 /coverage/
diff --git a/rollup.config.js b/rollup.config.js
index f0546fceb2..9ba2b667ea 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -67,6 +67,24 @@ export default [
 		]
 	},
 
+	/* motion.[m]js */
+	{
+		input: 'src/motion/index.js',
+		output: [
+			{
+				file: 'motion.mjs',
+				format: 'esm',
+				paths: id => id.replace('svelte', '.')
+			},
+			{
+				file: 'motion.js',
+				format: 'cjs',
+				paths: id => id.replace('svelte', '.')
+			}
+		],
+		external: id => id.startsWith('svelte/')
+	},
+
 	// runtime API
 	...['index', 'store', 'easing', 'motion', 'transition'].map(name => ({
 		input: `${name}.mjs`,
diff --git a/src/motion/index.js b/src/motion/index.js
new file mode 100644
index 0000000000..e0e9bcf1ae
--- /dev/null
+++ b/src/motion/index.js
@@ -0,0 +1,2 @@
+export * from './spring.js';
+export * from './tweened.js';
\ No newline at end of file
diff --git a/motion.mjs b/src/motion/spring.js
similarity index 54%
rename from motion.mjs
rename to src/motion/spring.js
index 395c678366..ebac993f06 100644
--- a/motion.mjs
+++ b/src/motion/spring.js
@@ -1,152 +1,5 @@
-import { writable } from './store';
-import { assign } from './internal';
-import { linear } from './easing';
-
-const tasks = new Set();
-let running = false;
-
-function run_tasks() {
-	tasks.forEach(task => {
-		if (!task[0]()) {
-			tasks.delete(task);
-			task[1]();
-		}
-	});
-
-	running = tasks.size > 0;
-	if (running) requestAnimationFrame(run_tasks);
-}
-
-function add_task(fn) {
-	let task;
-
-	if (!running) {
-		running = true;
-		requestAnimationFrame(run_tasks);
-	}
-
-	return {
-		promise: new Promise(fulfil => {
-			tasks.add(task = [fn, fulfil]);
-		}),
-		abort() {
-			tasks.delete(task);
-		}
-	};
-}
-
-function is_date(obj) {
-	return Object.prototype.toString.call(obj) === '[object Date]';
-}
-
-function get_interpolator(a, b) {
-	if (a === b || a !== a) return () => a;
-
-	const type = typeof a;
-
-	if (type !== typeof b || Array.isArray(a) !== Array.isArray(b)) {
-		throw new Error('Cannot interpolate values of different type');
-	}
-
-	if (Array.isArray(a)) {
-		const arr = b.map((bi, i) => {
-			return get_interpolator(a[i], bi);
-		});
-
-		return t => arr.map(fn => fn(t));
-	}
-
-	if (type === 'object') {
-		if (!a || !b) throw new Error('Object cannot be null');
-
-		if (is_date(a) && is_date(b)) {
-			a = a.getTime();
-			b = b.getTime();
-			const delta = b - a;
-			return t => new Date(a + t * delta);
-		}
-
-		const keys = Object.keys(b);
-		const interpolators = {};
-
-		keys.forEach(key => {
-			interpolators[key] = get_interpolator(a[key], b[key]);
-		});
-
-		return t => {
-			const result = {};
-			keys.forEach(key => {
-				result[key] = interpolators[key](t);
-			});
-			return result;
-		};
-	}
-
-	if (type === 'number') {
-		const delta = b - a;
-		return t => a + t * delta;
-	}
-
-	throw new Error(`Cannot interpolate ${type} values`);
-}
-
-export function tweened(value, defaults = {}) {
-	const store = writable(value);
-
-	let task;
-	let target_value = value;
-
-	function set(new_value, opts) {
-		target_value = new_value;
-
-		let previous_task = task;
-		let started = false;
-
-		let {
-			delay = 0,
-			duration = 400,
-			easing = linear,
-			interpolate = get_interpolator
-		} = assign(assign({}, defaults), opts);
-
-		const start = window.performance.now() + delay;
-		let fn;
-
-		task = add_task(() => {
-			const time = window.performance.now();
-			if (time < start) return true;
-
-			if (!started) {
-				fn = interpolate(value, new_value);
-				if (typeof duration === 'function') duration = duration(value, new_value);
-				started = true;
-			}
-
-			if (previous_task) {
-				previous_task.abort();
-				previous_task = null;
-			}
-
-			const elapsed = time - start;
-
-			if (elapsed > duration) {
-				store.set(value = new_value);
-				return false;
-			}
-
-			store.set(value = fn(easing(elapsed / duration)));
-			return true;
-		});
-
-		return task.promise;
-	}
-
-	return {
-		set,
-		update: (fn, opts) => set(fn(target_value, value), opts),
-		subscribe: store.subscribe
-	};
-}
+import { writable } from 'svelte/store';
+import { add_task, is_date } from './utils.js';
 
 function get_initial_velocity(value) {
 	if (typeof value === 'number' || is_date(value)) return 0;
diff --git a/src/motion/tweened.js b/src/motion/tweened.js
new file mode 100644
index 0000000000..020378408c
--- /dev/null
+++ b/src/motion/tweened.js
@@ -0,0 +1,113 @@
+import { writable } from 'svelte/store';
+import { assign } from 'svelte/internal';
+import { linear } from 'svelte/easing';
+import { add_task, is_date } from './utils.js';
+
+function get_interpolator(a, b) {
+	if (a === b || a !== a) return () => a;
+
+	const type = typeof a;
+
+	if (type !== typeof b || Array.isArray(a) !== Array.isArray(b)) {
+		throw new Error('Cannot interpolate values of different type');
+	}
+
+	if (Array.isArray(a)) {
+		const arr = b.map((bi, i) => {
+			return get_interpolator(a[i], bi);
+		});
+
+		return t => arr.map(fn => fn(t));
+	}
+
+	if (type === 'object') {
+		if (!a || !b) throw new Error('Object cannot be null');
+
+		if (is_date(a) && is_date(b)) {
+			a = a.getTime();
+			b = b.getTime();
+			const delta = b - a;
+			return t => new Date(a + t * delta);
+		}
+
+		const keys = Object.keys(b);
+		const interpolators = {};
+
+		keys.forEach(key => {
+			interpolators[key] = get_interpolator(a[key], b[key]);
+		});
+
+		return t => {
+			const result = {};
+			keys.forEach(key => {
+				result[key] = interpolators[key](t);
+			});
+			return result;
+		};
+	}
+
+	if (type === 'number') {
+		const delta = b - a;
+		return t => a + t * delta;
+	}
+
+	throw new Error(`Cannot interpolate ${type} values`);
+}
+
+export function tweened(value, defaults = {}) {
+	const store = writable(value);
+
+	let task;
+	let target_value = value;
+
+	function set(new_value, opts) {
+		target_value = new_value;
+
+		let previous_task = task;
+		let started = false;
+
+		let {
+			delay = 0,
+			duration = 400,
+			easing = linear,
+			interpolate = get_interpolator
+		} = assign(assign({}, defaults), opts);
+
+		const start = window.performance.now() + delay;
+		let fn;
+
+		task = add_task(() => {
+			const time = window.performance.now();
+			if (time < start) return true;
+
+			if (!started) {
+				fn = interpolate(value, new_value);
+				if (typeof duration === 'function') duration = duration(value, new_value);
+				started = true;
+			}
+
+			if (previous_task) {
+				previous_task.abort();
+				previous_task = null;
+			}
+
+			const elapsed = time - start;
+
+			if (elapsed > duration) {
+				store.set(value = new_value);
+				return false;
+			}
+
+			store.set(value = fn(easing(elapsed / duration)));
+			return true;
+		});
+
+		return task.promise;
+	}
+
+	return {
+		set,
+		update: (fn, opts) => set(fn(target_value, value), opts),
+		subscribe: store.subscribe
+	};
+}
\ No newline at end of file
diff --git a/src/motion/utils.js b/src/motion/utils.js
new file mode 100644
index 0000000000..986cec3ef4
--- /dev/null
+++ b/src/motion/utils.js
@@ -0,0 +1,36 @@
+const tasks = new Set();
+let running = false;
+
+function run_tasks() {
+	tasks.forEach(task => {
+		if (!task[0]()) {
+			tasks.delete(task);
+			task[1]();
+		}
+	});
+
+	running = tasks.size > 0;
+	if (running) requestAnimationFrame(run_tasks);
+}
+
+export function add_task(fn) {
+	let task;
+
+	if (!running) {
+		running = true;
+		requestAnimationFrame(run_tasks);
+	}
+
+	return {
+		promise: new Promise(fulfil => {
+			tasks.add(task = [fn, fulfil]);
+		}),
+		abort() {
+			tasks.delete(task);
+		}
+	};
+}
+
+export function is_date(obj) {
+	return Object.prototype.toString.call(obj) === '[object Date]';
+}
\ No newline at end of file