It's a side scroller game in which you hop over and underobstacles in order to reach the finish of the level, similar to old-school Mario Brothers. It contains basic gameplay mechanics (you just touch to leap at the appropriate moment) and relatively simple shapes, thus the name "Geometry Dash"

Geometry Dash is a series of five video games developed by Sweden-based developer Robert Topala, and published by his company, RobTop Games. 
The principal game, Geometry Dash, it is a rhythm-based platforming game which currently has 21 official levels and has more than 40 million online levels made by players. 
Check out the full version for new levels, soundtracks, achievements, online level editor and much much more!
Web/Link: https://geometrydash.io
How to Play:
Use mouse or WASD or arrow keys to control in this game.
Tips and Tricks:
You can play this game in full screen mode.
You can pause/resume/restart and turn the sound on/off on the game screen.