Cannon Ball
Cannon Ball (sometimes informally referred to as Morph Ball Invulnerability) is a special item in Metroid Prime 2: Echoes and Metroid Prime 3: Corruption that is temporarily given to Samus when she enters a designated morph ball cannon. It has three distinct properties:
- Total invulnerability while in Morph Ball
- An aura around the Morph Ball that deals 500,000 damage per frame
- This aura is capable of activating certain doors that were previously locked (though it cannot unlock currently locked doors) without needing to use a weapon against them
- Allows Samus to boost, even if she doesn't already have Boost Ball
Ordinarily, these effects are only given for a very short amount of time, as they are removed once Samus lands on standable ground, unmorphs, or touches the other side of the Morph Ball cannon. However, in a small amount of rooms, namely Workers Path and Sandcanyon, it is possible to keep these effects until the player resets the game or uses another morph ball cannon. This is possible under two conditions:
- The ability to use a morph ball cannon in a room while the game thinks you're in another room ("wrong room")
- The ability to unload the room that contains the cannon while using it
The reason this works is because if the game unloads the room while Samus has cannon ball, the game will not be able to remove cannon ball from her inventory, enabling her to keep it indefinitely. Getting cannon ball has applications in speedruns, mostly in any% during the adult phase of the Chykka boss fight in order to skip it in its entirety.
Rooms That Give Samus Cannon Ball
- Central Area Transport West
- Gathering Hall
- GFMC Compound
- Great Bridge
- Main Gyro Chamber
- Mining Station A
- Mining Station Access
- Mining Station B
- Portal Access A
- Reactor Core
- Sacred Bridge
- Sacred Path
- Sanctuary Entrance
- Sandcanyon
- Temple Access (Sanctuary Fortress)
- Torvus Plaza
- Watch Station
- Windchamber Gateway
- Workers Path
Cannons That Don't Give Samus Cannon Ball
Additionally, there are a small amount of rooms in the game that have Morph Ball cannons, but don't give Samus Cannon Ball.
- Hydrodynamo Station
- Transit Tunnel East
- Transit Tunnel South
- Transit Tunnel West
- Undertemple Shaft
- Undertransit One
- Undertransit Two
Workers Path Cannon Ball
This is the method most commonly used in speedruns, done after returning the Sanctuary energy. It starts by doing the Secret World in Sanctuary Energy Controller and wallcrawling to Worker's Path. Once transitioned, the scan point that activates the morph ball cannon must be scanned. Once scanned, climb back up and transition back into Sanctuary Temple. Now, ceiling warp into Worker's Path and use the Morph Ball cannon. Once the room unloads, you'll have successfully gotten cannon ball.
Sandcanyon Cannon Ball
This method takes advantage of the Bomb Guardian boss fight in Agon Temple. It works by activating the boss fight, performing the Agon Temple SW to get on top of the room, and using a charged Dark Beam shot to stun Bomb Guardian while vulnerable. The boss will cycle between being vulnerable and invulnerable while in this state, so as long as you keep freezing it, then you can continue to shoot Bomb Guardian from here. After the final shot is taken, you need to immediately ceiling warp back into Sandcanyon and take the morph ball cannon, making sure to hold down-right so that you fall below the room and unload Sandcanyon.
Watch Station Cannon Ball
This method takes advantage of Watch Station's connection with the room Central Area Transport West, which uses a proximity load. It is also the most difficult of the existing methods with current knowledge, but also the fastest in a TAS setting.
GFMC Compound Cannon Ball
TODO: Description and video