diff --git a/engine/Polygon.ts b/engine/Polygon.ts
index 880dd7c..3a64d96 100644
--- a/engine/Polygon.ts
+++ b/engine/Polygon.ts
@@ -1,4 +1,4 @@
-import { createVector, type Vector } from "#/engine/Vector.ts";
+import { createVector, setEdgeNormal, type Vector } from "#/engine/Vector.ts";
 
 export type Polygon = {
 	position: Vector;
@@ -24,25 +24,9 @@ export function updateAxes({ points, axes }: Polygon): void {
 
 	for (let i = 0; i < cap; i++) {
 		const pj = points[i + 1];
-
-		const nx = -(pj.y - pi.y);
-		const ny = pj.x - pi.x;
-
-		const invLen = 1.0 / Math.sqrt(nx * nx + ny * ny);
-
-		const axis = axes[i];
-		axis.x = nx * invLen;
-		axis.y = ny * invLen;
-
+		setEdgeNormal(axes[i], pi, pj);
 		pi = pj;
 	}
 
-	const nx = -(p0.y - pi.y);
-	const ny = p0.x - pi.x;
-
-	const invLen = 1.0 / Math.sqrt(nx * nx + ny * ny);
-
-	const axis = axes[cap];
-	axis.x = nx * invLen;
-	axis.y = ny * invLen;
+	setEdgeNormal(axes[cap], pi, p0);
 }
diff --git a/engine/Vector.ts b/engine/Vector.ts
index 3235880..5fe37d6 100644
--- a/engine/Vector.ts
+++ b/engine/Vector.ts
@@ -58,6 +58,15 @@ export function setDistanceNormal(normal: Vector, a: Vector, b: Vector): void {
 	}
 }
 
+export function setEdgeNormal(normal: Vector, a: Vector, b: Vector): void {
+	const nx = -(b.y - a.y);
+	const ny = b.x - a.x;
+	const inv = 1.0 / Math.sqrt(nx * nx + ny * ny);
+
+	normal.x = nx * inv;
+	normal.y = ny * inv;
+}
+
 export function getDotProduct(a: Vector, b: Vector): number {
 	return a.x * b.x + a.y * b.y;
 }
diff --git a/engine/system/processPhysics.ts b/engine/system/processPhysics.ts
index 0afa818..2ad4565 100644
--- a/engine/system/processPhysics.ts
+++ b/engine/system/processPhysics.ts
@@ -1,21 +1,33 @@
+import type { Circle } from "#/engine/Circle.ts";
 import $ from "#/engine/Scene.ts";
 import type { Vector } from "#/engine/Vector.ts";
 
-export type Collider = {};
+const CIRCLE = 0;
+const RECT = 1;
+const POLYGON = 2;
+
+type Shape = 0 | 1 | 2;
+
+export type Collider<T> = {
+	shape: Shape;
+	body: T;
+};
 
 export type Collision = {};
 
-export function moveAndCollide(
-	collider: Collider,
+export function moveAndCollide<T>(
+	collider: Collider<T>,
 	velocity: Vector,
 	delta: number,
-): Collision {}
+): Collision {
+	return {};
+}
 
 export function processPhysics(
 	ctx: CanvasRenderingContext2D,
 	delta: number,
 ): void {
-	for (const [id, collider] of $<Collider>("collider")!.entries()) {
+	for (const [id, collider] of $<Collider<unknown>>("collider")!.entries()) {
 		const position = $<Vector>("position")!.get(id);
 	}
 }