# http://lemmasoft.renai.us/forums/viewtopic.php?p=379109#p379109

screen countdown(timer_jump, time=5): # I set a default reaction time of 5 seconds
    timer time repeat False action [ Hide('countdown'), Jump(timer_jump) ]
    bar value AnimatedValue(0, time, time, time) at alpha_dissolve # assuming you're using the alpha_dissolve transform from the wiki

label start:
    "start test"
    show screen countdown("jump_label") # This uses the default time of 5.
#    show screen countdown("jump_label", 10) # This line, uncommented, will take 10 rather than 5 seconds.
    menu:
        "Choice 1":
            hide screen countdown
        "Choice 2":
            hide screen countdown

label jump_label:
    "You didn't choose anything."