Crystal Flash
Crystal Flash is a technique which fully replenishes Samus's energy.
The Crystal Flash can only be performed if Samus has less than 51 energy with empty (or no) Reserve Tanks, and can only be performed if Samus has 10 Missiles, 10 Super Missiles and 10 Power Bombs at the point of activation; however, because performing a Crystal Flash requires a Power Bomb explosion, you should consider it as requiring 11 Power Bombs to perform.
To activate the Crystal Flash (after planting a Power Bomb), L, R, down, and the shot button must be held as the Power Bomb's explosion ends, and Samus must be in the exact position (both horizontally and vertically) of the explosion, with zero vertical speed.
To perform a Crystal Flash with only 2 packs of Power Bombs collected, Samus needs to lay the Power Bomb (going down to 9), collect a Power Bomb drop (up to 10), and then return to the exact pixel where the Power Bomb was laid before the explosion vanishes to activate the Crystal Flash. An easy way to do so is to time the explosion right before an enemy reaches Samus, to get bounced off the ground and on landing collect the Power Bomb drop.
The Crystal Flash is utilized multiple times in Norfair/Lower Norfair during Reverse Boss Order runs, since none of the suit upgrades, which protect against heat, are collected.
Invulnerability
While the Crystal Flash is active, Samus will not be granted a period of invulnerability if contact with an applicable damage source is made, thus allowing enemies - especially mobile ones such as Zebbos - to potentially inflict tremendous damage.
