A new fan-made mod of Super Mario 64 allows you to create your own stages in the N64 classic.

"Mario Builder 64 is a toolbox letting you fulfil all of your SM64 dreams," say developers Rovertronic and Arthurtilly. "Play one of the numerous user-made levels, or create a course pushing your imagination (and hardware) to its limits!"

Once you've patched a copy of the original game with the hack, you can construct Super Mario 64 stages inside the ROM, which can then be played either via emulation or on original hardware.

"The level editor is easy to pick up but offers a lot of depth to advanced users - whether you're making a speedrun level, an 8-star course or an 8-bit calculator, the palette of over 100 parts will suit your needs," add the developers.

"The levels are endlessly customizable, with a vast selection of music, a theme editor for committed designers and an expanded interaction system ready to support any contraptions your mind envisions!"

There's a comprehensive guide here if you're looking to get started with this.