Great game. I love the twist you put to the damsel in distress. That in itself made me want to play and beat the game regardless of the game play.
Story: 3.00/5.00
The concept is great, as I mentioned before, but the story telling itself could use a little work. I understand that you were just testing this sort of game out though, so it's forgivable, but if you have time, make the next one better!
Graphics: 4.00/5.00
I'm not a huge fan of pixel art so that's why I'm not giving you a perfect 5, but as far as pixels go, it's great and everything is well made.
Gameplay: 3.50/5.00
Down to the core issue then. The game is too fast paced. Even the tutorial, which is generally slow, is too fast. Your tossed into the fray almost immediately, and while there is no penalty for losing a round, allowing you to restart as many times as you want, it's a little inconvenient. Now I'm not saying the sense of urgency is bad. It kept me on my toes, in fact, but you're tossed too suddenly into the wave. Perhaps if there's a countdown of five to ten seconds that allows you to place your traps before the enemies hurry in it would improve the game. It would allow better planning and leave you to your devices while the horde of unsuspecting heroes comes after you.
The diversity of enemies and traps was limited, but that again is forgivable as you've mentioned it's your first time stepping out of your comfort zone.
Level design was fairly limited as well. The only things that really varied were the slope lengths. The limited trap selection did up the difficulty level though so that was a nice touch.
Overall Score: 3.50/5.00