base_for_zoom = function(base)
	local n = base
	while scale(n) < base/2 do
		if scale(n*base) < base/2 then
			n = n*base
		else  -- scale linearly
			local n2 = n
			while scale(n2) < base/2 do
				n2 = n2+n
			end
			return n2
		end
	end
	return n
end

floor_to = function(n, base)
	return math.floor(n/base)*base
end

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

on.resize = function(w, h)
	Viewport.w, Viewport.h = w, h
end

	if App.mouse_down(1) then draw_grid() end

end

end