I was browsing another forum, and came across a way to activate an alignment test. By pressing Left, B, Down, A, Up (on the right pad) it brings up an alignment screen:

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Does anyone know of any other diagnostic screens? Also, is this function built into the hardware? I tried it on Wario Land and it only worked on the title screen, so is it part of the game, or do games have a method of enabling/disabling it?

It is a screen written into some games for the purpose of manually aligning the screens. AFAIK they appear at the title screen using the key combo. The only other possible screen is the IPD/focus adjustment screen that reappears on some games after booting (you somehow access it from the pause menu, can’t remember how).

Nothing is hardcoded into the VB. It’s all written into and stored in the ROMs.