Really cool idea! I think the introduction is kinda short, IMO you should allow the player to click away those windows instead of just making them disappear after a while. Also could need some more explanation like you have  double jump, your defense cards regenerate after a while, etc.

But I really love the idea of the damage calculation with the value of those cards! Well done!

It’s so harsh. I think with some platforms and jumping, it can be a little bit easier and just brilliant in the end. But even without - a cool and funny game.

Nice art! It is too fast for me, and I can hold it for 10-15 seconds only.

 I feel like my block cards are finished, and I didn't understand how to get new ones.