Move all engine stuff to GoRetro. Still many interactions between game and engine code that there should not be.

utils_collisions.go

@@ -0,0 +1,65 @@
+package GoRetro
+
+// Anything > 1 apart will collide (i.e. player wont collide with own projectile)
+const (
+	_                     = 0
+	LayerPlayer           = 1
+	LayerPlayerProjectile = 2
+	_                     = 3
+	LayerEnemy            = 5
+	LayerEnemyProjectile  = 6
+	_                     = 7
+	LayerScreenBounds     = 9
+)
+
+type Circle struct {
+	Center Vector
+	Radius float64
+	Layer  int
+}
+
+func circleOffset(c1 Circle, offset Vector) Circle {
+	return Circle{
+		Radius: c1.Radius,
+		Center: vectorAdd(c1.Center, offset),
+		Layer:  c1.Layer,
+	}
+}
+
+func collides(c1, c2 Circle) bool {
+	dist := vectorDistance(c1.Center, c2.Center)
+	collides := dist <= c1.Radius+c2.Radius
+	seperation := absInt(c1.Layer - c2.Layer)
+
+	// Don't collide elements that are on the same layer, or an adjacent one
+	if collides && (seperation > 1) {
+		return collides
+	}
+
+	return false
+}
+
+func CheckCollisions() error {
+	for i := 0; i < len(Elements)-1; i++ {
+		for j := i + 1; j < len(Elements); j++ {
+			for _, c1 := range Elements[i].Collisions {
+				for _, c2 := range Elements[j].Collisions {
+					if collides(circleOffset(c1, Elements[i].Position), circleOffset(c2, Elements[j].Position)) && Elements[i].Active && Elements[j].Active {
+						if (Elements[i].parentElement != Elements[j]) && (Elements[j].parentElement != Elements[i]) {
+							err := Elements[i].collision(Elements[j])
+							if err != nil {
+								return err
+							}
+							err = Elements[j].collision(Elements[i])
+							if err != nil {
+								return err
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return nil
+}