Fantastic game that I feel could be so much better with just a few mechanics tweaks. I would love for the money to carry over in between rounds, maybe earning a little extra if you stored a lot of money from the previous round. That would add a risk/reward factor about leaving unspent money.
Also when buying for upgrades you just cycle the shop for the one part you want to upgrade. Making the storage larger or only requiring 4 parts to upgrade would add more flexibility which lets players experiment with new parts.
Still great game though and I liked the battle animations.