If you remember playing Super Mario Bros 3 on your old SNES then you are going to LOVE this.
The last level before you fouhgt King Koopa was (in my memory) the hardest thing I had ever done at that point. Thanks to Geekologie.com for sharing this video of that final level remastered in 3D.
This is a Freddy Wong video reimagining the final level of Super Mario 3 (the tank and cannonball level) and Bowser confrontation in the first person. It's a sequel to the first level they made and took over 50-days of rendering to complete.