Level designs!! For me, I won't say hate, but it gets realllllyyyy tiresome after a few dozens.
First few levels....hehe this is so much fun
about the 10th level.....I am going to test and challange the players mind!
About the 20th level.......err...I'll just copy a few designs from the earlier and combine with some new.
After the 30th level.......For Each (Level): copy, paste, mix