New levels + HUGE performance

I figured out how to decrease the resolution of the shaders, and with that, ridiculous performance improvements without making the gameplay experience suffer. There are now 3 quality settings, with the lowest one being 100x cheaper than before while minimally impacting quality. 

5 new levels have been created, which will really challenge your skill. Some of them are quite difficult for me to finish, hopefully they are a fun challenge. Along with the 5 new levels, there is now a  level select screen and a save file to keep track of your progress and settings.