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

utils_vector.go

@@ -0,0 +1,20 @@
+package GoRetro
+
+import "math"
+
+type Vector struct {
+	X float64
+	Y float64
+}
+
+func vectorAdd(v1, v2 Vector) Vector {
+	return Vector{
+		X: v1.X + v2.X,
+		Y: v1.Y + v2.Y,
+	}
+}
+
+func vectorDistance(v1, v2 Vector) float64 {
+	return math.Sqrt(math.Pow(v2.X-v1.X, 2) +
+		math.Pow(v2.Y-v1.Y, 2))
+}