init -2 python:   
    w=0  
    def slide_function(trans, st, at):
        global w
        import math
        trans.yalign = w*math.sin(st*16*math.pi)
        return 0
transform vp:
    function slide_function
    repeat
label start:
    scene bg at vp
    show screen my_ekran
    "text"

screen my_ekran():
    if w>0:
        timer 0.3 action SetVariable ("w", 0)
    imagebutton:
        idle  "w.png"
        hover "w1.png"
        action SetVariable ("w", 0.02)