It's playable but its not very good. The cards always spawn in the same place so there is no element of surprise. The number of enemies stays the same for a while but then increases. It would have been a better difficulty curve if the number of enemies increased every level. And near the end of the game it became really slow which made the boss easy. Also the speed of the player's bullets is too fast and hard to aim. And using arrows to use cards is not good because I have to move my hand away from my mouse to use them (maybe 1, 2, 3, 4 would have worked better). I almost skipped playing the game because I was unaware it had to be played in fullscreen, but that seems to be a thing with all the Unity web games. If you work on these problems, your next game should turn out better.