function draw()
for i=0,200,1 do
tpt.drawline(5 * i * size, 0, 5 * i* size, 500);
tpt.drawline(0, i * 10* size, i * 10* size, 0);
tpt.drawline(i * 10 * size - 500, 0, i * 10 * size, 500);
end
end
function key(key_char)
if key_char == "v" then
tpt.register_step(draw)
end
if key_char == "n" then
tpt.unregister_step(draw)
end
if key_char == "u" then
size = size + 1;
end
if key_char == "j" then
size = size - 1;
end
end
size = 2;
tpt.register_keypress(key)