diff --git a/src/runtime/easing/index.ts b/src/runtime/easing/index.ts
index 7a762394c2..c23019b320 100644
--- a/src/runtime/easing/index.ts
+++ b/src/runtime/easing/index.ts
@@ -5,23 +5,23 @@ Distributed under MIT License https://github.com/mattdesl/eases/blob/master/LICE
 
 export { identity as linear } from 'svelte/internal';
 
-export function backInOut(t) {
+export function backInOut(t: number) {
 	const s = 1.70158 * 1.525;
 	if ((t *= 2) < 1) return 0.5 * (t * t * ((s + 1) * t - s));
 	return 0.5 * ((t -= 2) * t * ((s + 1) * t + s) + 2);
 }
 
-export function backIn(t) {
+export function backIn(t: number) {
 	const s = 1.70158;
 	return t * t * ((s + 1) * t - s);
 }
 
-export function backOut(t) {
+export function backOut(t: number) {
 	const s = 1.70158;
 	return --t * t * ((s + 1) * t + s) + 1;
 }
 
-export function bounceOut(t) {
+export function bounceOut(t: number) {
 	const a = 4.0 / 11.0;
 	const b = 8.0 / 11.0;
 	const c = 9.0 / 10.0;
@@ -41,43 +41,43 @@ export function bounceOut(t) {
 				: 10.8 * t * t - 20.52 * t + 10.72;
 }
 
-export function bounceInOut(t) {
+export function bounceInOut(t: number) {
 	return t < 0.5
 		? 0.5 * (1.0 - bounceOut(1.0 - t * 2.0))
 		: 0.5 * bounceOut(t * 2.0 - 1.0) + 0.5;
 }
 
-export function bounceIn(t) {
+export function bounceIn(t: number) {
 	return 1.0 - bounceOut(1.0 - t);
 }
 
-export function circInOut(t) {
+export function circInOut(t: number) {
 	if ((t *= 2) < 1) return -0.5 * (Math.sqrt(1 - t * t) - 1);
 	return 0.5 * (Math.sqrt(1 - (t -= 2) * t) + 1);
 }
 
-export function circIn(t) {
+export function circIn(t: number) {
 	return 1.0 - Math.sqrt(1.0 - t * t);
 }
 
-export function circOut(t) {
+export function circOut(t: number) {
 	return Math.sqrt(1 - --t * t);
 }
 
-export function cubicInOut(t) {
+export function cubicInOut(t: number) {
 	return t < 0.5 ? 4.0 * t * t * t : 0.5 * Math.pow(2.0 * t - 2.0, 3.0) + 1.0;
 }
 
-export function cubicIn(t) {
+export function cubicIn(t: number) {
 	return t * t * t;
 }
 
-export function cubicOut(t) {
+export function cubicOut(t: number) {
 	const f = t - 1.0;
 	return f * f * f + 1.0;
 }
 
-export function elasticInOut(t) {
+export function elasticInOut(t: number) {
 	return t < 0.5
 		? 0.5 *
 				Math.sin(((+13.0 * Math.PI) / 2) * 2.0 * t) *
@@ -88,17 +88,17 @@ export function elasticInOut(t) {
 				1.0;
 }
 
-export function elasticIn(t) {
+export function elasticIn(t: number) {
 	return Math.sin((13.0 * t * Math.PI) / 2) * Math.pow(2.0, 10.0 * (t - 1.0));
 }
 
-export function elasticOut(t) {
+export function elasticOut(t: number) {
 	return (
 		Math.sin((-13.0 * (t + 1.0) * Math.PI) / 2) * Math.pow(2.0, -10.0 * t) + 1.0
 	);
 }
 
-export function expoInOut(t) {
+export function expoInOut(t: number) {
 	return t === 0.0 || t === 1.0
 		? t
 		: t < 0.5
@@ -106,66 +106,66 @@ export function expoInOut(t) {
 			: -0.5 * Math.pow(2.0, 10.0 - t * 20.0) + 1.0;
 }
 
-export function expoIn(t) {
+export function expoIn(t: number) {
 	return t === 0.0 ? t : Math.pow(2.0, 10.0 * (t - 1.0));
 }
 
-export function expoOut(t) {
+export function expoOut(t: number) {
 	return t === 1.0 ? t : 1.0 - Math.pow(2.0, -10.0 * t);
 }
 
-export function quadInOut(t) {
+export function quadInOut(t: number) {
 	t /= 0.5;
 	if (t < 1) return 0.5 * t * t;
 	t--;
 	return -0.5 * (t * (t - 2) - 1);
 }
 
-export function quadIn(t) {
+export function quadIn(t: number) {
 	return t * t;
 }
 
-export function quadOut(t) {
+export function quadOut(t: number) {
 	return -t * (t - 2.0);
 }
 
-export function quartInOut(t) {
+export function quartInOut(t: number) {
 	return t < 0.5
 		? +8.0 * Math.pow(t, 4.0)
 		: -8.0 * Math.pow(t - 1.0, 4.0) + 1.0;
 }
 
-export function quartIn(t) {
+export function quartIn(t: number) {
 	return Math.pow(t, 4.0);
 }
 
-export function quartOut(t) {
+export function quartOut(t: number) {
 	return Math.pow(t - 1.0, 3.0) * (1.0 - t) + 1.0;
 }
 
-export function quintInOut(t) {
+export function quintInOut(t: number) {
 	if ((t *= 2) < 1) return 0.5 * t * t * t * t * t;
 	return 0.5 * ((t -= 2) * t * t * t * t + 2);
 }
 
-export function quintIn(t) {
+export function quintIn(t: number) {
 	return t * t * t * t * t;
 }
 
-export function quintOut(t) {
+export function quintOut(t: number) {
 	return --t * t * t * t * t + 1;
 }
 
-export function sineInOut(t) {
+export function sineInOut(t: number) {
 	return -0.5 * (Math.cos(Math.PI * t) - 1);
 }
 
-export function sineIn(t) {
+export function sineIn(t: number) {
 	const v = Math.cos(t * Math.PI * 0.5);
 	if (Math.abs(v) < 1e-14) return 1;
 	else return 1 - v;
 }
 
-export function sineOut(t) {
+export function sineOut(t: number) {
 	return Math.sin((t * Math.PI) / 2);
 }