This trigger takes an ID number as a required argument. It returns the number of projectiles currently owned by the player and having the specified ID number.

Format: NumProjID(exprn)

Arguments:

- exprn (int): Expression evaluating to an ID number.

Return type: int

Error conditions: If a negative ID is specified, then the ID defaults to 0. Returns 'Bottom' if exprn evaluates to 'Bottom'.

Example:

`trigger1 = NumProjID(1234) = 1
; Triggers if there the player currently owns exactly 1 projectile with the ID number 1234.`