local physics = require "physics"
physics.start()
physics.setGravity(0, 0)

local rock = display.newGroup(display.newCircle(0, 0, 30))

physics.addBody(rock, "kinematic", {radius = 30})

rock.x, rock.y = display.contentWidth, display.contentHeight * 0.25
rock:setLinearVelocity(-50, 15)

local function stick(event)
	local self, other = event.target, event.other
	self:removeEventListener('collision', stick)
	timer.performWithDelay(0,
		function()
			physics.removeBody(self)
			local x, y = self:localToContent(0, 0)
			other:insert(self)
			self.x, self.y = other:contentToLocal(x, y)
			timer.performWithDelay(5000, function(...) if self and self.removeSelf then self:removeSelf() end end)
		end
	)
end

local function spawn()
	local self = display.newCircle(display.contentCenterX, display.contentCenterY * 1.5, 6)
	self:setFillColor(0xFF, 0x00, 0x00)
	physics.addBody(self, 'dynamic', {radius = 5})
	self:setLinearVelocity(0, -150)
	self:addEventListener('collision', stick)
	local function monitor()
		local bounds = self and self.contentBounds
		if not bounds or bounds.xMin > display.contentHeight or bounds.xMax < 0 or bounds.yMax < 0 or bounds.yMin > display.contentHeight then
			if self and self.removeSelf then self:removeSelf() end
			Runtime:removeEventListener('enterFrame', monitor)
		end
	end
	Runtime:addEventListener('enterFrame', monitor)
end

timer.performWithDelay(500, spawn, 0)