You can use an ITEM SCRIPT on the Gun Item to direct to a Page that says “You’re out of Bullets” or the like when you don’t have Bullets. It would look something like this –
When you are keeping Track of Bullets as a Variable:
IF %BULLETS < 1 THEN
$DEST := @P100 (“Out of Bullets” Page
When you are keeping Track of Bullets as an ITEM:
IF $ITEMSTATE99 = 0 THEN
$DEST := @P100