I liked seeing my guy get older as time progressed. I would recommend giving the player a way to instantly spawn the next wave of enemies if there are no enemies left to fight, this would reduce time spent sitting around waiting.

Overall I like the game so far. I like the spawners and the enemy design, and the weapon choices, etc. I also really like the card mouseover effects. Only way I can think to improve that effect is if it were made a little less snappy so that when you first mouseover back and forth over the edge of a corner it takes a small moment for the card to reach it's ending position rather than snapping into place.

The music is also really well done, although It would be nice if it looped instead of vanishing forever after a single listen.

There also seems to be boundary issue. Can easily avoid fighting merely by picking a direction button to hold and then running off the screen. Might be a good idea to add some kind of border to prevent this.

I'm also not a big fan of the font, had to kind of squint at it and take a moment to figure out what it was saying.

Lastly, just an idea but instead of the timer counting down to the end of run with a score card, maybe this would be a good place to insert a boss fight.

I thought the game was perfectly reasonable. it's well enough animated and the controls are okay. my gripes would be that you didn't add a health bar, you can't see how long until the cooldown ends, and you don't tell the player the controls inside the game itself. the music is pretty cool, and that background is a little bit boring. tweaking any one of those would improve your work tenfold, also I see you used gamemaker? interesting choice of engine : )