Thank you for your comment! We're really aprecciating everyones feedback <3
This may clarify the way the game works, sorry for the long reply xD
Keep in mind that the combat only develops while you're playing the rhythm mini game. The enemies will hit you only when you don't have any creatures on board. This means that if you try to play too many units at the same time, you won't be able to survive the turn.
We recommend to take advantage of the immunity time at the start of each level and play only one creature. This way, the next turn you can play more creatures while the first one you played is taking the damage for you. Another suggestion is to try to build a snowball effect with the amout of units you play.
Now, the rhythm mechanic only affects the quality of the units stats, missing notes doesn't damage your health directly.
We hope you can give another shot and enjoy it!