A program can tell that it's running on PyBoy because the buttons always change right at vblank.

To reproduce:

1. Install PyBoy
2. Start the test ROM "Telling LYs?" (which I have precompiled for your convenience here)
3. Press all 8 buttons in any order
4. Watch the arrow sprite at the right side

Expect: Arrow moves after each press, followed

This would vastly help the Dev experience for game developers 😄 They cansimply host a local server that hosts their game, and the debugger can just try to grab it and auto run 😄

Needing to load ROMs from the filesystem every time is really annoying. We can easily cache them in localStorage or something.

Also the load cart UI should be rethought to allow for "included ROMs", "saved ROMs", or "load from FOO"