System Defender

System Defender  was a tower defense-style singleplayer game in Club Penguin Rewritten that was playable in the EPF Command Room. It was set in the EPF Mainframe Computer where you have to defend it from threats.

Levels
The game has six levels to choose from:

Red Cannon
The red cannon shoots fast but has low damage. It costs 50 energy and is best used for the beginning of all levels.

Orange Cannon
The orange cannon has a long range but only moderate damage and firing speed. It costs 125 energy and is best used in places where red and purple cannons would not be able to hit bots.

Purple Cannon
The purple cannon does a considerable amount of damage, but fires slowly. It deals a fatal blow to each bot it hits. It costs 200 energy and is best used against Purple and Boss bots.

Gears
Gears are items used to upgrade cannons. They are sometimes dropped by boss bots, but they can be bought for 500 energy. When used on red cannons, they add more shots per hit. For orange cannons, they increase damage and range. For purple cannons, they increase damage and add mini shots, which do a fair amount of damage and are somewhat faster than the regular shot of the cannon.

Red Bots

 * Red bots attack in large groups.
 * Best suited cannon: Red, because they can deal damage over a large area by firing quickly.

Orange Bots

 * Orange bots are the fastest bots but have low health.
 * Best suited cannon: Orange as it has a large range and can hit more bots.

Purple Bots

 * Purple bots can take lots of damage but are slow.
 * Best suited cannon: Purple as its beam of energy is powerful and you don't need a high rate of fire.

Energy
At the beginning of the game, you have a starting amount of 200 energy. Sometimes enemies drop extra energy, which can range from 5 to 50.

Weapon Prices

 * Red Cannon: 50
 * Orange Cannon: 125
 * Purple Cannon: 200
 * Gear: 500

Strategy

 * Use the 200 energy at the start to place 4 red cannons, except for the "Tracking Herbert" level, where you should put up 1 purple cannon on a corner.
 * U-turns and corners are the best places to put red cannons.
 * Once most of the U-turns and corners are filled with red cannons, build orange cannons separated evenly by each other.
 * Build multiple groups of orange cannons clustered in groups of 2-6. Orange cannons are extremely good at protecting against huge waves of bots.
 * Build purple cannons when the bosses start appearing in huge groups. They are the perfect anti-boss weapons.
 * When upgrading, upgrade one cannon fully before upgrading the next.
 * Try to completely upgrade each cannon.

Rewards
Some levels include Elite Medals as rewards; all include coins and stamps.

Trivia

 * The Ready For Duty Stamp was removed from the game as of January 24, 2018. This was due to a glitch that made it unavailable to all players.
 * The last Stamp Book polaroid of System Defender couldn't be seen until November 8, 2019. The required stamp amount for the last polaroid was reduced from 16 stamps to 13.
 * The level briefing for level five is a reference to the "Red Alert!" line from the Star Trek franchise.
 * System Defender used to be more difficult due to Club Penguin Rewritten running at a higher frame rate than Club Penguin, making it run faster than it should. This also affected Pizzatron 3000. It was still possible to complete, although extremely difficult. The frame rate was lowered on January 10, 2020.