This started out as a 36 hour challenge. I have since decided to turn it into a community-driven game, in that it is fully open source, and anyone can contribute!
Game link: Geometry Dash - Roblox
Github repository: https://github.com/nottirb/GeometryDash
Full gameplay footage: Roblox Geometry Dash - Full gameplay footage - YouTube
Full 36-hour development process:
1: https://youtu.be/LHJBhc_Sclo
2: https://youtu.be/ShQtB0-DrBs
3: https://youtu.be/DzJoPPW8-V4
4: https://youtu.be/vPcuSgcwbik
5: https://youtu.be/PlPtpU0AFkM
6: https://youtu.be/xap1GC8qcIg
7: https://youtu.be/Jjf3spi7L94
8: https://youtu.be/eTzFYoN4M5k
9: https://youtu.be/4r5kNLopFLw
10-1: https://youtu.be/83zA3GaEZVM
10-2: https://youtu.be/xsLHmSW8UTw
11: https://youtu.be/3vywYoVzr9c
12-1: https://youtu.be/LaZrz2j4yTA
12-2: https://youtu.be/bj3uk4DLRXA
13: https://youtu.be/CMtnhfmhIOY
14: https://youtu.be/VA3SZXORRZg