Breakable Tools - Need Help

I know it's not the point of this thread, but there's no way this is correct:

Code:

JSR $4B5A
AND #$2A       ;  1/42 chance of breaking
BNE no_break

$4B5A sets the accumulator to a random number from 0–255.
ANDing that with 42 doesn't give you a 1/42 chance. It gives you a 1/8 chance.

2A has 3 bits that are 1. ANDing sets all bits in the accumulator to except those 3. If the accumulator is now 0, the branch will be taken. The chance of those 3 bits being 0 is 1/2^3 = 1/8.

ANDing like this only works when the denominator is a power of 2. If you actually want a 1/42 chance, you need to do this:

Code:

LDA #$2A
JSR $4B65       ; set A to a random number between 0 and A-1
BNE no_break