That was a blast (both literally and metaphorically)! Love the effect of grenades blowing up and cacti being turned to smithereens.
Having the player stand still while the train moves is a small but smart move, that changes the gameplay nicely. I liked having to only focus on aiming, timing and throwing the grenades. The upgrades felt useful, powerful and had some good variation to play around with and encourage replay-ability.
This might be one of the most fun 3D games of the jam, nice work!