I used plain JavaScript - I don't know how to use any game engines. Game balance is something I had a hard time working on during the jam, so I kind of just guessed at the ideal values and hoped it would be fun. I find that it works out pretty well in the beginning, but as the game goes on the challenge disappears and the gameplay slows down a lot. I'm still not really sure how to tackle that issue, but I'm interested in working on the game a little more to see what I can do with more time. Do you have plans to work on your game further?