I started playing without reading the description and thought that the theme was in the controls, and once I started failing in the second level, oh boy, I got the surprise. The concept of leaving only one character alive was very clever, well done. Though I would recommend using an easier level to explain the concept of only one earlier, since the first level doesn't make the concept clear and the second level it's kinda hard by itself.
The visuals are simple but they work with the theme, lacking peraphs some adjustments in regards to visual feedback, like knowing the collision boundaries of the "waving" character. Overall the game plays really well and achieves what it had to: Showcaisng a game design that explores the theme of Only One. Good job guys.