How does your submission match the theme?
Any key trigger's the game's sole input, the spin attack. The attack has several effects. Inspired by Ikaruga's polarity mechanic, each spin alternates the weapon's nature and direction of attack, between clockwise spin (knock-back) and counterclockwise spin (absorption). As the names suggest, knock-back swats the target away, while absorption absorbs the target to restore health. The spin attack also has a third effect, a shield that appears briefly after each spin. The three effects (knock-back, absorption, and shield) are color-coded to match different enemy types. Striking an enemy with the matching color defeats it, while striking it with a different color causes some other effect. It is necessary not only to strike enemies with their matching color but also to leverage the effects of striking them with a non-matching color in order to progress in the game.

All that being said, obviously once you've tried the submission you'll notice that very little of the above is implemented, thanks to my noble but ultimately foolish decision to write my own engine. Oh, well. At least you know what I was thinking.

Third-party resources
jQuery

Contributors
J. Matthew Griffis

Source Code
https://github.com/jmatthewgriffis/gmtk-jam-2017