Fix vec2.angle to return degrees

src/vec2.test.ts

@@ -101,6 +101,14 @@ test('rotate', () => {
 })
 
 describe('angle', () => {
+	it('shoud work in the case of 0°', () => {
+		expect(vec2.angle([1, 0])).toEqual(0)
+	})
+
+	it('shoud work in the case of 90°', () => {
+		expect(vec2.angle([0, 1])).toEqual(90)
+	})
+
 	it('should work in the case of [-120°, 120]', () => {
 		const x = 1 / 2
 		const y = Math.sqrt(3) / 2

src/vec2.ts

@@ -464,7 +464,7 @@ export namespace vec2 {
 	 * Get the angle between two 2D vectors. If the second argument is omitted, it returns a signed angle relative to x axis.
 	 */
 	export function angle(a: vec2, b?: vec2) {
-		if (!b) return Math.atan2(a[1], a[0])
+		if (!b) return Math.atan2(a[1], a[0]) * Common.RAD2DEG
 
 		const [x1, y1] = a
 		const [x2, y2] = b