It seems like you are trying to make a menu that will pass when you press "A". Here is some code for that.
'YOUR CODE HERE BEFORE BUTTON PRESS
REPEAT
BR=BUTTON(2)
UNTIL BR==#A
'MORE CODE, INGAME MAYBE
Now, what does it mean?
BR=BUTTON(2)- This makes BR your return value. 2 (if i remember) should make it so it won't repeat the press.
The until makes it pass when the button A is pressed
It's actually pretty simple! The BUTTON function returns which buttons are being pressed in that exact moment in the form of a value. This means that BUTTON is more useful if you assign it to a variable. You can then operate this variable with logic gates and constants to determine which buttons are being pressed and build code, such as conditionals, with it.
also this game will be based off of super mario 64 but it will be 2D switching between both kinds of 2D (sidescroller and top-down) but it won't use mario characters even though its based off of super mario 64, i want most of it to be a suprise though