You've got a simple set of mechanics and a really great idea here. I loved how your tile-based raft was designed in a way that let the bombs poke holes in it without it losing its great visual identity. More "juice" like flashes, screen shakes, and audio cues would really go a long way towards taking this to the next level.
I'd also be curious to see how your game would play differently if you had shadows representing where the bombs were falling to help telegraph to players where to head to next. With a little more heads up on where they need to go, I bet you could do all kinds of interesting things with how the bombs drop where you've got multiple bombs dropping at once or them dropping in tight, pre-defined patterns/sequences to really ramp up the urgency and give more variety to the gameplay.
Thanks for making and sharing—this is one of my favorites so far!