extract phys

asteroids/phys.lua

@@ -0,0 +1,18 @@
+local phys = {
+    tau = 2 * math.pi
+}
+
+-- returns true if the two actors intersect
+function phys.intersects(actor1, actor2)
+    return (actor1.x - actor2.x) ^ 2 + (actor1.y - actor2.y) ^ 2 <= (actor1.radius + actor2.radius) ^ 2
+end
+
+-- updates the actor's location by applying the passage of time
+-- TODO spin
+function phys.update(actor, dt)
+    local dv = actor.speed * dt
+    actor.x = actor.x + math.cos(actor.angle) * dv
+    actor.y = actor.y + math.sin(actor.angle) * dv
+end
+
+return phys