4 files changed, 32 insertions, 9 deletions
diff --git a/dist/resources/entity/red_circle.json b/dist/resources/entity/red_circle.json
index c9479ae..65af16a 100644
--- a/dist/resources/entity/red_circle.json
+++ b/dist/resources/entity/red_circle.json
@@ -2,13 +2,9 @@
 	"sprite": "red_circle",
 	"collision": [
 		{
-			"type": "polygon",
-			"vertices": [
-				[-0.5, -0.5],
-				[-0.5, 0.5],
-				[0.5, 0.5],
-				[0.5, -0.5]
-			]
+			"type": "circle",
+			"center": [0, 0],
+			"radius": 0.46875
 		}
 	]
 }
diff --git a/src/controller/collision.ts b/src/controller/collision.ts
index e1bd9f9..a44ffa4 100644
--- a/src/controller/collision.ts
+++ b/src/controller/collision.ts
@@ -1,5 +1,6 @@
 import { Collision } from '../model/data/collision';
 
+import { Circle } from '../math/circle';
 import { Collidable } from '../math/collision';
 import { LineSegment, Movement } from '../math/line';
 import { Point } from '../math/point';
@@ -26,6 +27,11 @@ export function mkCollision(collision: Collision[]): Collidable[] {
 				ret.push(new Point(vec2.clone(v)));
 				prev = v;
 			}
+			break;
+
+		case 'circle':
+			ret.push(new Circle(vec2.clone(c.center), c.radius));
+			break;
 		}
 	}
 
diff --git a/src/math/circle.ts b/src/math/circle.ts
new file mode 100644
index 0000000..f4e855a
--- /dev/null
+++ b/src/math/circle.ts
@@ -0,0 +1,15 @@
+import { Collidable } from './collision';
+import { Movement } from './line';
+import { Point } from './point';
+
+import { vec2 } from 'gl-matrix';
+
+export class Circle implements Collidable, Point {
+	private pointCollide = Point.prototype.collide;
+
+	constructor(public readonly p: vec2, public readonly r: number) {}
+
+	public collide(out: vec2, move: Movement, r: number): boolean {
+		return this.pointCollide(out, move, r + this.r);
+	}
+}
diff --git a/src/model/data/collision.ts b/src/model/data/collision.ts
index 5008fa3..29d0879 100644
--- a/src/model/data/collision.ts
+++ b/src/model/data/collision.ts
@@ -1,6 +1,12 @@
-export interface CollisionPolygon {
+export interface PolygonCollision {
 	readonly type: 'polygon';
 	readonly vertices: Array<[number, number]>;
 }
 
-export type Collision = CollisionPolygon;
+export interface CircleCollision {
+	readonly type: 'circle';
+	readonly center: [number, number];
+	readonly radius: number;
+}
+
+export type Collision = PolygonCollision | CircleCollision;