diff --git a/src/runtime/internal/loop.ts b/src/runtime/internal/loop.ts
index e1bf02033a..9335fcaa68 100644
--- a/src/runtime/internal/loop.ts
+++ b/src/runtime/internal/loop.ts
@@ -28,24 +28,20 @@ let pending_inserts = false;
 const run_timed = (now: number) => {
 	/* Runs every timed out task */
 	let last_index = timed_tasks.length - 1;
-	while (last_index >= 0 && now >= timed_tasks[last_index].timestamp) timed_tasks[last_index--].callback(now);
+	while (~last_index && now >= timed_tasks[last_index].timestamp) timed_tasks[last_index--].callback(now);
 	if (pending_inserts) {
-		for (
-			let i = 0, j = last_index, this_task: TimeoutTask, that_task: TimeoutTask;
-			i < pending_insert_timed.length;
-			i++
-		)
+		for (let i = 0, j = 0, this_task: TimeoutTask, that_task: TimeoutTask; i < pending_insert_timed.length; i++)
 			if (now >= (this_task = pending_insert_timed[i]).timestamp) this_task.callback(now);
 			else {
 				/* moves each task up until this_task.timestamp > task.timestamp */
-				for (j = last_index; j > 0 && this_task.timestamp > (that_task = timed_tasks[j]).timestamp; j--)
+				for (j = last_index; ~j && this_task.timestamp > (that_task = timed_tasks[j]).timestamp; j--)
 					timed_tasks[j + 1] = that_task;
-				timed_tasks[j] = this_task;
+				timed_tasks[j + 1] = this_task;
 				last_index++;
 			}
 		pending_inserts = !!(pending_insert_timed.length = 0);
 	}
-	return (running_timed = !!(timed_tasks.length = last_index));
+	return (running_timed = !!(timed_tasks.length = last_index + 1));
 };
 const unsafe_loop = (fn) => {
 	if (!next_frame_length) raf(run);
@@ -73,15 +69,15 @@ export const setAnimationTimeout = (callback: () => void, timestamp: number): Ta
  */
 export const useTween = (
 	run: (now: number) => void,
-	stop: () => void,
+	stop: (now: number) => void,
 	end_time: number,
 	duration = end_time - now()
 ): TaskCanceller => {
 	let running = true;
 	unsafe_loop((t) => {
 		if (!running) return false;
-		t = 1 - (end_time - t) / duration;
-		if (t >= 1) return run(1), stop(), false;
+		t = (end_time - t) / duration;
+		if (t >= 1) return run(1), stop(t), false;
 		if (t >= 0) run(t);
 		return running;
 	});
diff --git a/src/runtime/internal/scheduler.ts b/src/runtime/internal/scheduler.ts
index d62cc2ea4d..b1274fe8f3 100644
--- a/src/runtime/internal/scheduler.ts
+++ b/src/runtime/internal/scheduler.ts
@@ -4,14 +4,13 @@ import { resolved_promise } from './environment';
 const dirty_components = [];
 
 let update_scheduled = false;
-export function schedule_update(component) {
+export const schedule_update = (component) => {
 	dirty_components.push(component);
 	if (!update_scheduled) (update_scheduled = true), resolved_promise.then(flush);
-}
-export function tick() {
-	if (!update_scheduled) (update_scheduled = true), resolved_promise.then(flush);
-	return resolved_promise;
-}
+};
+export const tick = () =>
+	update_scheduled ? resolved_promise : ((update_scheduled = true), resolved_promise.then(flush));
+
 export const binding_callbacks = [];
 const render_callbacks = [];
 const seen_callbacks = new Set();
@@ -20,38 +19,55 @@ export const add_render_callback = (fn) =>
 
 const flush_callbacks = [];
 export const add_flush_callback = (fn) => void flush_callbacks.push(fn);
+const measure_callbacks = [];
+export const add_measure_callback = (fn) => void measure_callbacks.push(fn);
 
 let flushing = false;
 export function flush() {
 	if (flushing) return;
 	else flushing = true;
 
-	for (; dirty_components.length; ) {
+	let i = 0,
+		j = 0,
+		$$,
+		before_update,
+		dirty;
+
+	// RUN LOGIC, CANCEL STYLES
+	do {
 		// update components + beforeUpdate
-		for (let i = 0, $$; i < dirty_components.length; i++) {
+		for (i = 0; i < dirty_components.length; i++) {
 			({ $$ } = set_current_component(dirty_components[i]));
 			if ($$.fragment === null) continue;
-			const { update, before_update, dirty, after_update } = $$;
-			update();
-			for (let j = 0; j < before_update.length; j++) before_update[j]();
+			$$.update();
+			for (j = 0, { before_update } = $$; j < before_update.length; j++) before_update[j]();
+			({ dirty } = $$);
 			$$.dirty = [-1];
 			if ($$.fragment) $$.fragment.p($$.ctx, dirty);
-			render_callbacks.push(...after_update);
+			render_callbacks.push(...$$.after_update);
 		}
 		dirty_components.length = 0;
 
 		// update bindings in reverse order
-		for (let i = binding_callbacks.length - 1; i >= 0; i--) binding_callbacks[i]();
+		i = binding_callbacks.length;
+		while (i--) binding_callbacks[i]();
 		binding_callbacks.length = 0;
 
 		// afterUpdate
-		for (let i = 0; i < render_callbacks.length; i++) render_callbacks[i]();
+		for (i = 0; i < render_callbacks.length; i++) render_callbacks[i]();
 		render_callbacks.length = 0;
 		seen_callbacks.clear();
-	}
+	} while (dirty_components.length);
+
+	update_scheduled = false;
 
-	for (let i = 0; i < flush_callbacks.length; i++) flush_callbacks[i]();
+	// STYLE MEASURE CHANGES
+	for (i = 0; i < measure_callbacks.length; i++) flush_callbacks.push(measure_callbacks[i]());
+	measure_callbacks.length = 0;
+
+	// APPLY STYLE CHANGES
+	for (i = 0; i < flush_callbacks.length; i++) flush_callbacks[i]();
 	flush_callbacks.length = 0;
 
-	update_scheduled = flushing = false;
-}
\ No newline at end of file
+	flushing = false;
+}
diff --git a/src/runtime/internal/style_manager.ts b/src/runtime/internal/style_manager.ts
index 0051ba6618..f409d9c1a8 100644
--- a/src/runtime/internal/style_manager.ts
+++ b/src/runtime/internal/style_manager.ts
@@ -1,5 +1,5 @@
 import { element } from './dom';
-import { raf } from './environment';
+import { raf, now } from './environment';
 const enum SVELTE {
 	RULE = `__svelte_`,
 	STYLESHEET = `__svelte_stylesheet`,
@@ -43,22 +43,23 @@ function hash(str: string) {
 	while (i--) hash = ((hash << 5) - hash) ^ str.charCodeAt(i);
 	return hash >>> 0;
 }
-const gen = (t, step, css) => {
+const gen = (step, css) => {
 	let rule = '{\n';
-	for (; t < 1; t += step) rule += `${100 * t}%{${css(t)}}\n`;
+	for (let t = 0; t < 1; t += step) rule += `${100 * t}%{${css(t)}}\n`;
 	rule += `100% {${css(1)}}\n}`;
 	const name = SVELTE.RULE + hash(rule);
 	return [name, `@keyframes ${name} ${rule}`];
 };
-export function animate_css(css: (t: number) => string, node: HTMLElement, duration: number, t = 0) {
-	const [name, rule] = gen(t, duration / (FRAME_RATE || calc_framerate()), css);
+export function animate_css(css: (t: number) => string, node: HTMLElement, duration: number, delay = 0) {
+	const [name, rule] = gen(Math.max(1 / 1000, (FRAME_RATE || calc_framerate()) / duration), css);
 	const [stylesheet, rules] = add_rule(node);
 	if (!rules.has(name)) {
 		rules.add(name);
 		stylesheet.insertRule(rule, stylesheet.cssRules.length);
 	}
 	const previous = node.style.animation;
-	node.style.animation = (previous ? previous + ', ' : '') + `${duration}ms linear 0ms 1 normal both running ${name}`;
+	node.style.animation =
+		(previous ? previous + ', ' : '') + `${duration}ms linear ${delay}ms 1 normal both running ${name}`;
 	running_animations++;
 	return () => {
 		const prev = (node.style.animation || '').split(', ');
diff --git a/src/runtime/internal/transitions.ts b/src/runtime/internal/transitions.ts
index d2b90c3d1a..8f476be7d6 100644
--- a/src/runtime/internal/transitions.ts
+++ b/src/runtime/internal/transitions.ts
@@ -4,12 +4,12 @@ import { setAnimationTimeout, useTween } from './loop';
 import { animate_css } from './style_manager';
 import { custom_event } from './dom';
 import { TransitionConfig } from '../transition';
-import { add_render_callback, add_flush_callback } from './scheduler';
+import { add_measure_callback, add_render_callback } from './scheduler';
 import { Fragment } from './Component';
 
-function startStopDispatcher(node: Element, direction: boolean) {
-	add_render_callback(() => node.dispatchEvent(custom_event(`${direction ? 'intro' : 'outro'}start`)));
-	return () => node.dispatchEvent(custom_event(`${!direction ? 'intro' : 'outro'}end`));
+function startStopDispatcher(node: Element, is_intro: boolean) {
+	node.dispatchEvent(custom_event(`${is_intro ? 'intro' : 'outro'}start`));
+	return () => node.dispatchEvent(custom_event(`${is_intro ? 'intro' : 'outro'}end`));
 }
 
 const outroing = new Set();
@@ -47,65 +47,73 @@ export function transition_out(block: Fragment, local?: 0 | 1, detach?: 0 | 1, c
 	block.o(local);
 }
 
-const eased = (fn: (t: number) => any, easing: (t: number) => number) => (easing ? (t: number) => fn(easing(t)) : fn);
-const runner = (fn: (t0: number, t1: number) => any, reversed: boolean) =>
-	reversed ? (t: number) => fn(1 - t, t) : (t: number) => fn(t, 1 - t);
+const eased = (fn: (t: number) => any, easing: (t: number) => number, start, end) => (t: number) =>
+	fn(start + (end - start) * easing(t));
+//easing ? (!is_intro ? (t: number) => fn(easing(t)) : (t: number) => fn(1 - easing(1 - t))) : fn;
+const runner = (fn: (t0: number, t1: number) => any, is_intro: boolean) =>
+	is_intro ? (t: number) => fn(t, 1 - t) : (t: number) => fn(1 - t, t);
+const mirror = (fn, easing, is_intro) => {
+	const run = is_intro ? (t) => fn(1 - t, t) : (t) => fn(t, 1 - t);
+	return easing ? (is_intro ? (t) => run(1 - easing(1 - t)) : (t) => run(easing(t))) : run;
+};
 type TransitionFn = (node: HTMLElement, params: any) => TransitionConfig;
 export function run_transition(
 	node: HTMLElement,
 	fn: TransitionFn,
 	is_intro = true,
 	params = {},
-	reversed_from = -1
+	left_duration = 0,
+	prev_left = 0
 ): StopResetReverse {
-	let config = fn(node, params);
+	let config;
 	let running = true;
 
 	let cancel_css;
 	let cancel_raf;
 	let dispatch_end;
 	let end_time;
+	let t;
+	let start_ratio;
 
 	const group = outros;
 	if (!is_intro) group.r++;
 
-	function start({ delay = 0, duration = 300, easing, tick, css }: TransitionConfig) {
+	const start = ({ delay = 0, duration = 300, easing, tick, css }: TransitionConfig) => {
 		if (!running) return;
-		const start_time = ~reversed_from ? reversed_from : now() + delay;
-		end_time = start_time + duration;
-		if (css)
-			cancel_css = animate_css(
-				runner(eased(css, easing), is_intro),
-				node,
-				duration,
-				(end_time - start_time) / duration
-			);
+		t = duration - (left_duration > 0 ? left_duration : 0);
+		end_time = now() + t;
+		start_ratio = 1 - easing((t - prev_left) / duration);
+		if (css) cancel_css = animate_css(eased(runner(css, is_intro), easing, start_ratio, 1), node, t, 0);
 		dispatch_end = startStopDispatcher(node, is_intro);
 		cancel_raf = tick
-			? useTween(runner(eased(tick, easing), is_intro), stop, duration, end_time)
+			? useTween(eased(runner(tick, is_intro), easing, start_ratio, 1), stop, end_time, t)
 			: setAnimationTimeout(stop, end_time);
-	}
-	function stop(reset_reverse?: 1 | -1) {
-		if (!is_intro && 1 === reset_reverse && config && 'tick' in config) config.tick(1, 0);
+	};
+
+	const stop = (end_reset_reverse?: number | 1 | -1) => {
 		if (!running) return;
 		else running = false;
 		if (cancel_css) cancel_css();
 		if (cancel_raf) cancel_raf();
-		if (dispatch_end) dispatch_end();
+		if (t > end_time && dispatch_end) dispatch_end();
 		if (!is_intro && !--group.r) for (let i = 0; i < group.c.length; i++) group.c[i]();
-		if (!~reset_reverse) return run_transition(node, fn, !is_intro, params, end_time);
-		else if (!~reversed_from) running_bidi.delete(node);
-	}
-	// @ts-ignore
-	if (typeof config === 'function') add_flush_callback(() => start((config = config())));
-	else start(config);
+		if (!~end_reset_reverse)
+			return run_transition(node, () => config, !is_intro, params, end_time - now(), left_duration);
+		else if (left_duration) running_bidi.delete(node);
+	};
+
+	add_measure_callback(() => {
+		config = fn(node, params);
+		return () => start(typeof config === 'function' ? (config = config()) : config);
+	});
+
 	return stop;
 }
 export type StopResetReverse = (reset_reverse?: 1 | -1) => StopResetReverse;
 const running_bidi: Map<HTMLElement, StopResetReverse> = new Map();
 export function run_bidirectional_transition(node: HTMLElement, fn: TransitionFn, is_intro: boolean, params: any) {
 	let cancel;
-	if (running_bidi.has(node)) running_bidi.set(node, (cancel = running_bidi.get(node)(-1)));
+	if (running_bidi.has(node) && (cancel = running_bidi.get(node)(-1))) running_bidi.set(node, cancel);
 	else running_bidi.set(node, (cancel = run_transition(node, fn, is_intro, params, -1)));
 	return cancel;
 }
diff --git a/src/runtime/internal/utils.ts b/src/runtime/internal/utils.ts
index b9b3604f91..1b727bd4ff 100644
--- a/src/runtime/internal/utils.ts
+++ b/src/runtime/internal/utils.ts
@@ -136,8 +136,3 @@ export const has_prop = (obj, prop) => Object.prototype.hasOwnProperty.call(obj,
 export function action_destroyer(action_result) {
 	return action_result && is_function(action_result.destroy) ? action_result.destroy : noop;
 }
-export const minmax = (min: number, max: number) => (value: number) => (min > value ? min : value > max ? max : value);
-export const clamper = (min: number, max: number) =>
-	min !== -Infinity || max !== Infinity
-		? (fn: (value: number) => any) => (value: number) => (min > (value = fn(value)) ? min : value > max ? max : value)
-		: (fn: (value: number) => any) => fn;
diff --git a/src/runtime/transition/index.ts b/src/runtime/transition/index.ts
index 837ae16e51..800e1288b2 100644
--- a/src/runtime/transition/index.ts
+++ b/src/runtime/transition/index.ts
@@ -58,16 +58,14 @@ export function fly(
 	const style = getComputedStyle(node);
 	const target_opacity = +style.opacity;
 	const transform = style.transform === 'none' ? '' : style.transform;
-
 	const od = target_opacity * (1 - opacity);
-
 	return {
 		delay,
 		duration,
 		easing,
 		css: (t, u) => `
-			transform: ${transform} translate(${(1 - t) * x}px, ${(1 - t) * y}px);
-			opacity: ${target_opacity - od * u};`,
+			transform: ${transform} translate(${u * x}px, ${u * y}px);
+			opacity: ${target_opacity - od * u}`,
 	};
 }