Defold tanks spawn

player.lua

go.property("spawn_interval", 2) 
go.property("max_speed", 100)

function init(self)
	msg.post(".", "acquire_input_focus")

	self.moving = false
	self.firing = false
	self.input = vmath.vector3()
	self.dir = vmath.vector3(0, 1, 0)
	self.speed = self.max_speed
	self.timer = self.spawn_interval
    self.score = 0
end

function final(self)
	msg.post(".", "release_input_focus")
end

function update(self, dt)
	if self.moving then
		local pos = go.get_position()
		pos = pos + self.dir * self.speed * dt
		go.set_position(pos)
	end

	if self.firing then
		local angle = math.atan2(self.dir.y, self.dir.x)    -- [1]
		local pos = go.get_position()
		local rot = vmath.quat_rotation_z(angle)            -- [2]
		local props = { dir = self.dir }                    -- [3]
		factory.create("#rocketFactory", pos, rot, props)   -- [4]
	end
	
	self.input.x = 0
	self.input.y = 0
	self.moving = false
	self.speed = self.max_speed
	self.firing = false

	self.timer = self.timer - dt
	if self.timer < 0 then
		local angle = math.atan2(self.dir.y, self.dir.x)    -- [1]
		local pos = go.get_position()
		pos.x = math.random(550) + 50
		pos.y = math.random(400) + 50
		local rot = vmath.quat_rotation_z(angle)            -- [2]
		factory.create("#tankFactory", pos, rot)   -- [4]
		self.timer = self.spawn_interval
	end
end

player_on_message.lua

function on_message(self, message_id, message, sender)
	if message_id == hash("contact_point_response") then
		local currentpos = go.get_position()
		-- 2.1 is a strange magic number here... TODO
		local newpos = currentpos + (message.normal * message.distance * 2.1)
		go.set_position(newpos)
	end
end