System Defender is a Tower Defense-style mini-game that is playable in the EPF Command Room. It is set in the EPF Mainframe Computer where you have to defend it from threats. The game has six levels to choose from:
- Tracking Herbert
- Herbert Attacks
- Test Bots
- Klutzy Attacks
- Ultimate Protobot
- Enemy Bots
The red cannon shoots fast but has low damage. It costs 50 energy and is best used for the beginning of all levels.
The yellow 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.
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 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 yellow 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 attack in large groups.
- Best suited cannon: Red, because they can deal damage over a large area by firing quickly.
- Orange bots are the fastest bots but have low health.
- Best suited cannon: Yellow as it has a large range and can hit more 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.
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.
- Red Cannon: 50
- Yellow Cannon: 125
- Purple Cannon: 200
- Gear: 500
- 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 yellow cannons separated evenly by each other.
- Build multiple groups of yellow cannons clustered in groups of 2-6. Yellow 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.
Some levels include Elite Medals as rewards — all include coins and stamps.
|Garbage Disposal||Destroy 100 enemies in 1 level|
|Bug Overload||Protect the EPF mainframe from rogue bugs|
|Strategic Success||Destroy 100 enemies without upgrading cannons|
|Mono Mechanic||Complete a game with only one type of cannon|
|Tactical Pro||Destroy 100 enemies without taking damage|
|Master Mechanic||Fill every open socket with a cannon|
|Herbert Attacks||Complete the level 'Herbert Attacks'|
|Klutzy Attack||Protect the EPF mainframe from Klutzy|
|Strategic Master||Destroy 250 enemies without upgrading|
|Tactical Ace||Destroy 250 enemies without taking damage|
|Test Bot Trio||Protect the EPF mainframe from the Test Bots|
|Protobot Attack||Protect the EPF mainframe from Ultimate Protobot|
|Track Herbert||Complete the level 'Track Herbert'|
- System Defender is more difficult due to a bug making it run faster than it should. This remains to be fixed, however each and every level is still possible to be finished.
- The stamp Ready for Duty was removed from the game as of January 24, 2018. This was most likely because of a glitch that made it unavailable to all players. It is unknown if the stamp will ever return or not.