This is fun! The graphics are very cute, especially the way the enemies walk. There could do with being some more environmental details, but it is understandable that their isn't considering this is a compo entry.
On the gameplay front, the only real problem is that the aiming feels a little off - I guess there is some ideal distance at which you will hit an enemy in the centre of the screen, but if they are too close you have to aim slightly left. I also think the card element is underdeveloped in favour of the FPS side of the gameplay. I think in most card based games you would be able to choose from a selection of cards each turn, and it would be really cool to see something like that introduced to this game, if you continue to develop it, along with more card types, more status effects, cards that act on the player etc.
Overall, a very nice looking game in which I can see a lot of potential, good work!