The AntiCheat

Anticheat is a built-in sensor that checks if players are doing something that isn't humanly possible. Usually, the purpose of the anticheat is to stop cheaters from cheating.

Defence
In Defence levels, there used to exist a feature where the cannonballs will generate in the centre of the cannon instead of in the head. Using this feature and having fast button-mashing skills will grant the player immunity to failing the levels. This was fixed shortly after the creator found it out himself.

Boss Battles
In Boss Battle levels, the maximum damage one can possibly deal is ~10,500 (using the Ninja Star and Life Drain weapons simultaneously). Going any higher than this will simply deal no damage to the boss until the value that stores the damage goes back to a reasonable amount.

If one manages to circumvent the damage value limits, such as editing the values in the damage output or using another function, it hides a sneaky little trick. It will INSTANTLY kill the player without doing any damage to the boss, though it flashes when hit as if it was a normal weapon, rendering an 'instakill' impossible, unless the boss's health is below 10,000, making instakills of the first and second world bosses possible.

''NOTE: On rare occasions, attempting to instakill a powerful boss will result in both the player and the boss despawning, leaving nothing but the background and the interface. The player can still move around and shoot, but pausing will not work and the only way to get around this is to wait for the time to run out or reload the game.''

Hit Counter
Attempting to survive more than 22 hits, such as with custom health regeneration code or setting the health value to an insane amount on starting a level, it will trigger some functions:
 * At 22 hits, the boss stops taking damage from almost all attacks. This can be circumvented with the Ninja Star.
 * At 50 hits, the player will not be able to move or attack anymore. This can be circumvented by pausing and un-pausing.
 * At 100 hits or more, the player's HP is set to 1, allowing for some instant kills from enemy attacks.