Mother Brain Room/Low Ammo

The following are notes on optimal routing of Lower Tourian including Mother Brain Room, in the absense of tools for or knowledge of Zebetite Skip, and without assuming 10 Missile Zebetite Kill.

Basics

Tourian Recharge Room allows refilling Missiles to Samus' maximum capacity available, and is the only available source of additional ammo damage in Lower Tourian. If the player lacks sufficient ammo to fight through the whole of Lower Tourian in one run, the Recharge Room must be visited one or more times.

The player's final count of Super Missiles that can be used in Lower Tourian is locked in after entering Big Boy Room, and de facto locked in after defeating Metroid Room 4, from where it is not meaningful to backtrack for more refills, if the player otherwise has sufficient ammo for dealing with Lower Tourian by any means.

Any health that is sufficient for surviving Rainbow Beam (3 tanks with Varia Suit, 6 tanks without) is also sufficient for easily damage-tanking Blue Hopper Room. The ability to defeat Blue Sidehoppers with five Super Missiles thus serves no proper gameplay purpose and should be considered a part of the game's environmental storytelling, used to demonstrate to a first-time player the scale of danger posed by the Super Metroid.

In other words, Samus' maximum capacity of Super Missiles is less meaningful than the actual count left in her possession. With care, it is regardless usually possible to bring her maximum capacity or something close to it into Lower Tourian.

Doors, Zebetites and Mother Brain's glass jar are the three obstacles in Lower Tourian standing between Samus and Mother Brain. All of these disappear permanently once destroyed, and the player can backtrack after these tasks to refill Missiles.

Basic numbers

Missiles do 100 damage, Super Missiles do 300 damage.

Early Lower Tourian

Red doors in Seaweed Room and Rinka Shaft require 5 Missiles or 1 Super Missile to unlock.

• With lowest loadouts, the former door is usually not a consideration, as the player likely also has not performed Baby Skip and must refill at least Samus' health anyway. The optimal strategy is thus to open the door with Missiles before the 1st refill.

  Taking further damage in Lower Tourian but before the Mother Brain fight is not strictly speaking required, and with 4 Reserve Tanks (+ at least one Energy Tank proper) it is technically possible to skip refilling health at Tourian Recharge Room entirely. This is unlikely to be ever practical.

• In loadouts with some lenience, using a Super Missile on red doors is often preferrable to to using Missiles, which is both faster and leaves 2 more Missiles for dealing damage.

The Gadora in Tourian Eye Door Room requires 3 Missiles or 1 Super Missile to defeat. The latter is faster and thus generally preferrable, except in very low Missile loadouts, where Super Missiles must be saved either for dealing with Zebetites effectively without excess backtracking or for getting through MB1.

No substantial threat is posed by the Gadora or in Rinka Shaft. With at least 15 Missiles, it is quite doable to unlock all three doors already before the 1st refill. However, with any loadout that leaves 5 or more Missiles of lenience with Zebetites (e.g. 25+5), the Rinka Shaft door will be optimally instead unlocked on the first Zebetite pass-thru. In any loadout with 8 or more (e.g. 30+0 or 20+5), the same holds for the Gadora.

Mother Brain room

Zebetites have 1000 health but regenerate over time, and thus killing one requires minimally any of the following ammo combinations:

11 Missiles   •   8 Missiles + 1 Super Missile   •   5 Missiles + 2 Super Missiles   •   2 Missiles + 3 Super Missiles   •   4 Super Missiles

where 2+3 is optimal in speed and damage dealt, has the least risk of mis-hitting Rinkas or bullets, and should be preferred whenever Super Missiles are available in sufficient numbers. 4 Super Missiles by contrast wastes 100 damage that could have been used on other Zebetites or Mother Brain.

Mother Brain's glass jar requires 6 projectiles to break or 18 projectiles to completely destroy. This makes no difference between Missiles and Super Missiles.

• Since 10 Super Missiles suffice to defeat MB1, given any ammo loadout between 8+10 and 0+18, the player should simply do this instead. Indeed many loadouts too low to fully destroy the jar, such as 6+10 or 0+16, suffice also.
• If the player has an ammo loadout with at least 18 ammo but less than 10 Super Missiles, i.e. ranging from 17+1 to 7+9, it can be optimal to finish destroying the jar using also some Super Missiles, before returning to defeat MB1 with a refilled supply of Missiles.

Mother Brain's 1st phase ("MB1") has 3000 health and does not take damage from Charge Beam. Defeating her requires minimally any of the following Missile + Super Missile combinations:

• (With a Missile cap of 30): 30+0   •   27+1
• (With a Missile cap of 25): 24+2   •   21+3
• (With a Missile cap of 20): 18+4
• (With a Missile cap of 15): 15+5   •   12+6
• (With a Missile cap of 10): 9+7   •   6+8
• (With a Missile cap of 5): 3+9
• (With a Missile cap of 0): 0+10

Later phases of Mother Brain

Mother Brain's 2nd phase has 18000 health, and in low ammo situations must be defeated primarily with Charge Beam. In its absense, she requires ammo ranging from 180 Missiles to 60 Super Missiles (the latter number only obtainable in randomizers and other mods). Combined with ammo required for MB1 gives requirements of ammo between 210+0 and 0+70 to get through the fight.

• Saved up Missiles provide higher DPS than any Charge Beam combination without Plasma Beam. (To check: also higher than plain Charge+Plasma?)
• Saved up Super Missiles provide higher DPS than any Charge Beam combination short of optimal usage of Full Beam (Charge+Ice+Wave+Plasma).
• These DPS saves will usually not justify adding additional Missile refill trips to one's Lower Tourian route, but could be possible. The best case would be in otherwise no-refill branches which begin fading to mid-range ammo loudouts. E.g. taking a refill with a 80+0 loadout allows bringing up to 50 Missiles into the fight — equivalent to 84 plain Charge Beam shots, 56 Charge+Ice shots.

Mother Brain's 3rd phase must be defeated with Hyper Beam. No ammo calculations matter by this point.