Blaster Master Area 2 and 6 Bosses

Blaster Master Area 2 and 6 Bosses (and other strategies)
by ZeroNoin

The boss of Area 6 in Blaster Master (the long-armed green claw boss) is problematic in a speedrun as it often fails to die soon after the grenade glitch removes all its health.  It staying alive with zero health is often described as a zombie state.  This can also occur on the boss of Area 2, but is very uncommon.

Through much observation of tendencies in various scenarios, I have come to the conclusion that most likely so much code is being executed each frame during this boss that it usually fails to initiate the death sequence -- this causes the zombie state.
Given this, the primary way to reduce the zombie state is to minimize the amount of code being executed each frame after unpausing the grenade glitch.  Here are things that tend to accomplish this:
1.  Do not fire your weapons (either gun or grenade) during the zombie state.
2.  Get away from the boss to minimize hitbox routines.  Try not to have any of your character's hitbox on either the same X or Y positions as any of the boss's main body's hurtbox.
3.  Get away from the boss's claws to minimize claw projectile routines.  If your character is in front of and/or about 2 tiles to the side of or about 2 tiles behind either claw, this routine is executed.  Since the claws are positioned on the right side of the screen when the fight begins, it also helps to stand left of the boss's hitbox and pause the grenade glitch on an early frame in the fight.
4.  Stop moving your character and release all buttons.  Also try to tap Pause quickly and not hold it at the end of the grenade glitch.
5.  Only have one grenade fired during the grenade glitch.
6.  Try not to stand so close to the boss during the grenade glitch.  Perhaps launch the grenade from a distance; this can be a straight long throw (Right + A), or even better, a diagonal long throw (Right + Up + A); this will place your character in a position of lower code execution immediately after unpausing the grenade glitch.

Example strategy - Try to get the pause of the grenade glitch early, then hold Down + Left before unpausing the grenade glitch, unpause (when the hit sound changes) and walk about 2-3 tiles diagonally, then release the control pad and all buttons.  If you need to dodge projectiles, quickly move and stop again in a good position.  This seems to keep the zombie state (if it happens) below 2 seconds about 80%+ of the time, and below 5 seconds seemingly all the time.  Moving away from the boss in another direction (such as Up + Left) may also work well.  Sometimes throwing one or two lone grenades while moving away can help, but I think on average it tends to make things worse.  It would probably take a great deal of work figuring exactly what tends to work best.

Once the boss actually stops and enters the death sequence, I have found that periodically firing grenades tends to make the death sequence go faster.  Do not mash grenades as this makes it take much longer.  You can also instead responsively fire grenades when you see slowdown, which is visible in the boss slowly or not changing color, and visible in your character walking slower than usual (lag).

Bosses can freeze up in the death sequence because the explosions have an RNG factor.  Random Number Generation does a sequence of modifications on the RNG value stored in $0013 of the RAM.  The generation can enter a cycle where the same set of values are being generated, and those values can either slow or stop the death sequence.  Since grenades also use RNG for the position of explosion graphics, they also cause RNGeneration; grenade RNG very effectively breaks cycles in death sequence RNG; grenade explosion graphics need to be visible for their RNG to happen.  Other actions can also break this cycle seemingly by changing the lag; the most effective actions in breaking cycles in order seem to be grenades, pause/unpause, bullets (especially into walls), and moving.  Interrupting this cycle is only useful while explosion graphics are happening.

Periodically throwing grenades during the death sequence of the bosses of Area 4 and 7 seems to have a neutral effect.  On the bosses of Area 1, 3, 5, and 8 (second boss) it has a random effect, saving or losing time, but I suspect on average losing a slight amount of time due to lag; I recommend only firing a grenade on these bosses if you happen to see the death sequence slow down.  I'm not sure if always or sometimes throwing grenades is better for the bosses of Area 2 and 8 (first boss).

There perhaps exists better strategies than these for Boss 6, but they would likely require mapping much of the game's code to find.  Music and sound effects may play a factor here, but manipulating those is likely difficult (aside from weapon sounds).

Demonstration Video - https://youtu.be/ugemoIn41PU

The boss of Area 2 is not nearly as laggy as the similar boss of Area 6, with its shorter arms and fewer projectiles.  The best strategy seems to be throwing a grenade upward into the pause grenade glitch at the start of the fight.  You may or may not want to fire grenades to speed the death sequence.  This is probably the most simple and easy boss in the run.

Credits
Pause Grenade Glitch - one of the oldest and most well-known video game glitch discoveries