Yep, alot of it was shaders, the enemy dying is using pixel sorting shader, the rainbow and speed line shaders are layered in the upgrade screen and more... It was mostly open source code, I hace very little experience with them, I hope to understand them better in the future though!
But yeah the balancing did need some more work and I would have loooved a boss fight against the AI: I mean I have all its sprites and animations readily available!
Thank you for playing and for your feedback!