Projectile limit

Older games had a limit of 1 or 2 simultaneously existing projectiles from same shooter with the player incapable of shooting more until one or both had been destroyed (hit something).

Notes:
* Promotes player behaviour where they only shoot when the projectile is guaranteed to have limited live time (e.g. a wall right behind the target), allowing the player to shoot again faster in case they miss their target.
* Has the effect that your gun shoots extremely fast at point blank range but extremely slow when far away from your target.
* There's usually no explanation for this, and even if there's one, it's likely BS.
* Although this also affects your enemies, you rarely see them taking advantage of it (they don't shoot faster at close range).
* Some rare games would delete the oldest projectile instead of block shooting, causing an effect where the projectiles disappear into thin air if you shoot too fast.
* The limits may vary with weapons.

Limitations:
* Does not include slow weapons that give similar effect, but the speed remains unchanged regardless how long the previous projectile lasts.
* Sensible cases of projectile limits should not count, such as with actively guided weapons, boomerangs, or weapons that imitate a returning hammer (you have only one thrown weapon that returns to you).