I saw this forum was Zero'd out so I figured I would throw something in here.
I originally learned about Geometry Dash by watching Dashie ( [You must be registered and logged in to see this link.]
) back in the day.
The music is awesome and its great to pull out on my phone when I'm waiting in line somewhere.
My 7 year old loves it and has been enjoying beating some of the levels or progressing his completion % on the harder stages. Its great for hand eye / ear coordination too! Its been around for a good while now, but its a goodie!