There are many interesting aspects of the game, including how the boss could destroy towers, etc. The rogue-like RNG aspect also makes every playthrough different from the others. The game music is also great and well composed. The clouds and plane objects flying around also adds elements to the environment, making it more engaging and feel like I'm not the only person in the game.
This game has great potential and I think that the game can be improved further by adding certain other mechanics like coin farms to upgrade towers, or being able to customise the card deck etc.