First, you select your difficulty. Also, you can select your icon. You start with one icon, but you can unlock more by beating levels. Then, you can press the up arrow to jump. Avoid spikes. Also avoid hitting blocks from the side or below. When your icon turns into a ship, press up to fly. Yellow circles let you jump midair, and blue circles change gravity. Lastly, try to get to the flag at the end of each level. If you touch it, you complete the level. Please post in the comments whether you'd like new levels, longer levels, or practice mode (checkpoints).
Images: Geometry Dash Wiki Idea: Geometry Dash Level mechanics: The impossible game revamped (a scratch project by shadowspear1.) Music: Stereo Madness by Forever Bound, Back on Track by DJVI, Can't let go by DJVI, Ultimate Destruction by TMM43. Beginner is to help you practice jumping over spikes. Yes, I know it kinda sucks, but this was my first project. Update 1.1: added beginner.