use std, canvas

w = 800   h = 600
window("canvas example 2", w, h);
color(#ffffff)
frect(0, 0, w, h)

step = rand(20)
color(#0000ff)
for y = 0, y < h, y += step {
    line(0, y, w, y)
}
for x = 0, x < w, x += step {
    line(x, 0, x, h)
}
repaint();