Thanks for the review! Yeah, the sampler uses godot's timer node to play and I'm aware of the problem you mentioned, I just didn't know how to work around it. The timer doesn't update until it has finished a loop, so even if you up the tempo it will wait the 6 seconds or what remains when changing from 10bpm.
The offset slider is a really cool idea, but I'm not sure how I'd implement that. When I get to work on it a bit more after the jam I'll experiment with that a bit, but I can't promise much. As for expanding it, I already have many ideas of what sounds and instruments to add. The bonuses for using specific BPMs isn't a bad idea, I'll also think about it.