This is a cool game! At first, I thought the ticking sound was just coming from the bomb in the background, but then I realized I was actually using up my limited steps, which was a really neat way to communicate the mechanic. The concept is pretty relatable too (I hate when I receive giant bombs in my mail 😭)
I think some background music could add a lot to the atmosphere. Also, since the bomb is so huge, I think the explosion could have a little more impact than just a flashbang (maybe with some screen shake or explosion effects??) Anyways, great job!