Suggestion:
1-make the controller vibrate at the same rythm as the metronome
2-add the option to replace the deny with a ruined orgasm whenever that would occur (by asking too often to cum for example)
3- a cum countdown instead of "you have x minutes to cum", and you have 2-3 attempts where if you fail you get denied/ruined orgasm (unlimited countdowns but you have to ruin it at the end)