Nice concept and it plays well, I find it little bit boring though, upgrades in between tests would be nice. Also, because of how it's organized (with the timer and patterns and all) it's mostly a matter of just clicking on the boss and occasionally dodging. But not too many tactics, because you will run out of time. Balance is a bit off.
Thanks for pointing that out, we have actually halved the difficulty 4 times until now due to playtesters finding the game hard. Difficulty in this sort of games is a bit hard to do right because of the seemingly non-existing skill ceiling.
As for the upgrades, that's definitely a cool idea which we had in mind. Perhaps future updates might have something like that although it would be challenging to reward players with a noticeable power-up that doesn't make the game progressively easier instead of harder. Simply making them some stat changes would just cancel out with the rising difficulty and giving players a shield or parry would make the gameplay too easy and RNG reliant.
If they ever are to come it would most likely be in the form of consumables to allow recovering from certain mistakes, such as a high damage bomb (if the timer runs low) or a health recovery item if the player comes close to dying.