To play, you just have to hold your mouse down on the button and lift it off once the line to the orbiting circle starts to blink. (There's not a much better way to explain this so if you're confused just try playing) Red circles are enemies, if they collide with a dot that's bigger than them they will get destroyed and you will get points. You also get points for placing dots. Hold down the button for larger dots and more points. More levels means more dots placed each time.
Based on the video below by Jonas Tyroller: https://www.youtube.com/watch?v=7L1B5YaxxoA The video is about how to make clicking a button fun, and I recreated their game as best as I could :)