merged from branch, working but custom operators not implemented
landscape view, added result to equation
operators working.
Now need to make flash cards repeat if missed, otherwise remove from deck.
can add or remove operators.  redeals deck.  started to add toggles, but not implemented.
implemented switches.  don’t think the mastery is working.  note: this is set for limited integer range for debugging

need to implement max integer.

bug.  fails when runs out of cards.
adding and removing operators is working,
hack - blank cards when not enough to deal.  blank cards have a “=“
bug - not enough cards are left available?  check where availability is set
warning - check the whole mastery, missing and available labels for correctness