App attempting to access item -1 of a list, I don't get why

This looks like MineSweeper.

  • Don't hardwire number limits, instead use length of list.

  • There are < and > options buried in those comparison blocks, if you use the pulldown. Don't make your tests paper thin, make them solid walls

  • Use the Blocks Editor right click option to use external sockets, so your blocks don't look like the plastic holders of six packs of soda cans

  • Use the Clean Up Blocks option, to allow your scroll wheel access to all the blocks without having to zoom out to space.

  • Use a table (lists of lists) for your Buttons, so you can address by row and column:

Samples:

Randomized selection: