I am honestly not satisfied with the physics in this game, simply because I wrote them from scratch and not using an existing physics library. It contains a lot of hacks and sometimes makes bombs move unexpectedly.
Explosion timing is calculated by how close the other bomb exploded. And there is actually an indicator for their timing. They blink faster when timer decreases and they become fully red without blinking when they are about to explode.
Anyways thanks for the feedback! It’s really appreciated!