Yeah, I focused a lot on polishing graphics (which was also my aim to experiment here with the visuals, like what I can do with shaders or particle effects)
Additionally I have a strong computer / GPU, so I didn't have the lag / crash issues that much (except for the tutorial level, which even my computer wasn't able to handle in a few cases).
Also, I must say, especially the last 2-3 levels are really difficult. The very last even still for me.