function love.load()
	screenWidth = love.graphics.getWidth()
	screenHeight = love.graphics.getHeight()
	canvas = love.graphics.newCanvas(screenWidth, screenHeight)
end

function love.draw(dt)
	-- draw to canvas
	love.graphics.setCanvas(canvas)
	local w = screenWidth / 2
	love.graphics.setBlendMode('alpha')
	-- draw cyan rect on the left
	love.graphics.setColor(0, 255, 255)
	love.graphics.rectangle('fill', 0, 0, w, screenHeight)
	-- draw yellow rect on the right
	love.graphics.setColor(255, 255, 0)
	love.graphics.rectangle('fill', w, 0, w, screenHeight)
	love.graphics.setCanvas()
	-- blit canvas to screen
	love.graphics.clear()
	love.graphics.setBlendMode("alpha", "premultiplied")
	love.graphics.draw(canvas)
	-- after drawing canvas to screen, left rect is green
end