Ret's Escape Puzzle World is a Super Mario Bros. 1 ROM Hack created by Excel in 2004. The levels were designed to puzzle and frustrate players, sometimes by gruesome level design, and other times, tricky puzzles.
There is also a secret fourth world after you manage to complete the hack, along with a hidden warp pipe in World 4-4 leading to a mysterious level that tests your Big Mario skills. View them here or here.
This TAS created by me solves the levels quickly and beats Zejoant’s TAS by about 9 seconds due to major optimizations in various levels.
You can also view the TASes mashed together here.