It shows a timer in the intermission of when you should use the gateway to stack.
Compared to other WAs that do the same I've implemented the following:
-A counting down sound from 3 to 1
-An "action sound" on 0 to signal that you should click the gateway now
-Support for both BigWigs & DBM sounds, it will detect the installed bossmod and uses available sounds
-Custom options to select the sound channel and toggle the action sound on/off