 = sx;
			mousemove_sy = sy;
			draw_canvas();
		}
	}, false);

	canvas.addEventListener('pointerdown', function(e) {
		const canvas_rect = canvas.getBoundingClientRect();
		const sx = e.clientX - canvas_rect.left;
		const sy = e.clientY - canvas_rect.top;
		mousedown_sx = sx;
		mousedown_sy = sy;
		mousemove_sx = mousedown_sx;
		mousemove_sy = mousedown_sy;
		canvas.releasePointerCapture(e.pointerId);
	}, false);

	canvas.addEventListener('wheel', function(e) {
		if(e.shiftKey) {
			const scale = Number(do