draw_grid = function()
	love.graphics.setColor(0.8, 0.8, 0.8)
	local xlo, xhi = sx(0), sx(Viewport.w)
	local ylo, yhi = sy(0), sy(Viewport.h)
	local base = base_for_zoom(100)
	xlo, xhi = floor_to(xlo, base), floor_to(xhi, base)+base
	ylo, yhi = floor_to(ylo, base), floor_to(yhi, base)+base
	for x = xlo, xhi, base do
		love.graphics.line(vx(x), 0, vx(x), Viewport.h)
	end
	for y = ylo, yhi, base do
		love.graphics.line(0, vy(y), Viewport.w, vy(y))
	end
end