Novice/young programmers seem to love making OS mockups as a first exercise. This phenomenon even predates web apps: I remember an entire scene consisting of MS-DOS GUIs made with QuickBasic. Hundreds of them - many clones of Windows 95 or Mac OS. There's a site that hosts a bunch of them still: http://qbasicgui.datacomponents.net/

I remember someone making one for an MS-DOS text mode game creation system called MegaZeux. They called it Airborne OS. It was spawned by the enthusiasm around Windows 95/98 at the time, though the result is rather wonky, especially if you're not used to how MegaZeux games typically operate. For example, the cursor is actually the player character and can only move with the arrow keys.

1999 version: https://www.digitalmzx.com/show.php?id=12

2000 version: https://www.digitalmzx.com/show.php?id=13

That's exactly how aOS started. Wasn't quite my first exercise, but was among the first few things I ever made.

I have a little snapshot of how it looked back then, at https://aaronos.dev/AaronOS_Old/

Also: http://www.virtualdesktop.org/

I love collections like these. So cool to see what different people have done with the concept.

That’s a really cool collection.