Lines

// create
ymin = room_height*3/5 //adjust
ymax = room_height
ydiv = ymax-ymin
nlines = 6 //adjust
spd = 7 //adjust

var I:
for (I=1; I<=nlines; I++)
{
yd[I] = ydiv *I / nlines
}

//draw

draw_set_color(c_lime) //c_green?
var I:
for (I=1; I<=nlines; I++)
{
yd[I] = (yd[I] + spd) mod ydiv
draw_set_alpha(yd[I]/ydiv)*(0.9+random(0.1))
//adjust flicker, should add up to 1
draw_line(0, yd[I], room_width, yd[I])
}
//code for vertical lines should stay the same