Fun game. Cute graphics. Frustrating upgrade system.
The upgrades can't really be engaged with until you have a few battles under your belt, so the mention of them at the beginning doesn't align with game flow. Mildly stymieing.
Upgrades increasing in power cost never feels good to the player. Upgrades should be all positive. If you're going to increase the resource cost to use an upgrade, then at the very least, leave the option to use the lower grade versions so that the more expensive version becomes optional instead of feeling like a trap. Repair lvl 3 feels particularly egregious in this regard.
The stat increases with upgrade levels is nice, but not being able to see what a level up will grant stats-wise is annoying.
Infect ability doesn't really feel worth it action economy-wise.
Having to land all the QTEs for the multi-hit attacks or take the full damage feels wrong. Partial success shouldn't be all or nothing. In that same vein, the basic Pulse would probably feel better to upgrade into a multi-hit variant instead of more damage. Infect could become more or less potent depending on successes. Same for healing. Multiple successes doesn't have to translate into a 1:1 multiplier on potency. Something like 1 success = 100%, 2 successes = 150%, 3 successes = 200%, or 50%, 75%, 100% would be fine.