set $vel0 .9
set $vel1 .6

set $countto 3
set $counter 0
set $step 1
set $reset 0

lo $playup
hi $playdown

@loop

on $playup $vel0
wait 1
off $playup


lt $counter $countto @skip2
set $counter $reset
lo $playup
goto @loop
@skip2

add $counter $step

up $playup
valid $playup @skip1
lo $playup
@skip1

on $playdown $vel1
wait 1
off $playdown

down $playdown
valid $playdown @skip3
hi $playdown
@skip3

goto @loop