Blaster Master and MetaFight Gameplay Differences

Blaster Master and MetaFight Gameplay Differences
by ZeroNoin

The original version of Blaster Master for the NES in North America was Chô Wakusei Senki Metafight for the Famicom in Japan.  It features a number of differences, including a story that makes more sense.  This document centers on differences I have found so far in gameplay.

Continues
Blaster Master allows 4 continues.  (Value is stored at $037E in RAM.)
MetaFight allows infinite continues.
This allows for more Death Warps in MetaFight.
This also makes MetaFight more event and marathon-friendly than Blaster Master.

Reset
When Reset is pressed and a game is started in MetaFight, the player's items and bosses killed before the reset remain to start the game.
This can very much be used for Reset Warps when the item is grabbed following boss kills in Areas 3 and 6.
Bosses are marked as killed at the start of the fade at the end of their explosion.
Items are marked as collected at the start of the fade after being picked up.
Reset Warps can replace Death Warps (such as those following Areas 3 and 6) to save additional time.
This is also something that somewhat breaks standard Character Control Timing as the player can collect all the game's items, kill the Area 8 boss, reset, start a game, and travel directly to the final boss.
Bosses killed is cleared at the start of the fade at the end of the final boss's explosion.
Items are cleared when Start is pressed at the end of the credits.
Items and kills actually endure resets in Blaster Master (as seen in the demos), but clears them at the start of a new game.
This also makes MetaFight somewhat more event and marathon-friendly than Blaster Master.

Fade Start Glitches
Fades are transitions where the palette progressively increases or decreases the brightness of colors over 7 or 8 frames.
A number of fades in MetaFight can be glitched by pressing Start during them.
These include boss spawns, warps after picking up items, and the title screen.
Blaster Master fixed all these glitches by disabling Start during fades.

Boss Fade Pause Glitch
MetaFight has a glitch where if the game is paused during the fade into black on bosses, some strange things happen.
The pattern table (tiles for the shapes of graphics) for the previous room will load.
When the game is paused during the boss, the item screen will load (this means the Grenade Pause Glitch does not work here).
Much of the overhead area can be traveled while the boss is active; pausing and unpausing can refresh boundaries allowing for further travel; sometimes walls can be traveled through, along with some screen-wrapping and background desync.
The door to the boss room will continue to allow exiting and entering.
The boss can still be killed outside the boss room, sometimes being easier to fight there.
This is particularly useful on the Area 5 boss, and sort of useful on the final boss.
Both versions contain a similar Boss Fade Exit Glitch where the player exits the boss room right as the fade begins.
The Fade Pause Glitch is much easier; Fade Exit has a 1 frame window; Fade Pause has an 8 frame window, the first of those frames being the same as the frame for the Fade Exit.
The Fade Pause Glitch allows for mashing Pause before the fade happens, time wasted on pausing; if there is an early Fade Exit input, the room must be entered again and restarted.
The Fade Pause Glitch on the Area 5 boss is overall about 1 second faster than the Fade Exit Glitch as the boss room can be entered again more quickly.

Item Fade Pause Glitch
If Start is pressed during the fade following an item pickup in MetaFight, the warp to the start of the area is cancelled.

Random Number Generation
The RNG value at $0013 in the RAM shuffles every frame in MetaFight, while in Blaster Master it only shuffles when it is applied to something; the RNG shuffle can happen multiple times per frame in Blaster Master.
I suspect the developers thought it was an improvement for Blaster Master to have RNG only called when needed.
While this probably makes the game do less overall work through the course of the game, it unfortunately means that more work tends to be done when it matters most.
Because more work tends to be done on RNG when enemies are on the screen, and because enemies are the main source of lag, Blaster Master is more prone to lag frames; grenades also tend to cause more lag because of the RNG in their graphics.
Also the RNG in MetaFight tends to be smoother and more random, while in Blaster Master it can be more cyclical and prone to forming unlikely patterns.
Patterns in RNG in Blaster Master often include grenade explosion graphics, Flyer spawning (Hover farming), Area 5 boss movements, boss death sequences, and Wall Walker movements.
Because of its cyclical RNG patterns, Zombie and Death Sequence Glitches are more likely to occur in Blaster Master.

Lag
So far in testing, I estimate Blaster Master has 15-30% more lag frames than MetaFight.
In preliminary testing, MetaFight averages something like 200 lag frames per minute (about 5.5%), Blaster Master averages about 250 lag frames per minute (about 6.9%); the difference between the two seems to be about 1 second per minute.
Exact lag difference will vary with player performance, especially in how quickly the player destroys enemies.

Screen Scrolling
I suspect the scrolling of the screen takes less code, and is therefore less laggy, but I'm not sure about this for the time being.

Area 4 Key Room
MetaFight has an interesting part here where the player must exist the tank, climb a long ladder, fall 18 blocks distance, and grab a small ladder to prevent fall death.
The player can continue holding Right to walk off the ledge and fall the correct distance, and grab the ladder by pressing A when the character overlaps it.
There is about a 4-frame window for pressing A during this fall; pressing Up or Down does not grab the ladder during a fall.
Blaster Master changed this design to be a series of platforms and ladders, a series of short drops and climbs to the ground; a few extra turrets were added.
This part is usually skipped during a speedrun in both versions using the Tunnel Reversal Glitch.
It does however make death warps from the key room to the start of Area 4 a bit slower.

Title Screen and Intro
The title screen for MetaFight has a Fade Start Glitch where if Start is hit during the fade, it will lock and prevent a game start.
The Fade Start Glitch can happen between frames 8 and 14 following reset or power-on.
The Fade Start Glitch can be undone (like during a reset run) by doing another reset and not doing the glitch yet again.
On the title screen for both, Start has a turbo function like Left and Right do on the item screen.
It takes about 25 frames for the turbo to kick in, and this turbo can cause the Fade Start Glitch if built before a reset.
For both games, it is about 1/4 second faster to time pressing Start after the fade instead holding it and waiting on turbo.
A MetaFight game can be started on frame 15, while a Blaster Master game can be started on frame 16.
A Blaster Master game actually begins from power-on or reset 6 frames faster than MetaFight.

Lives
MetaFight loads lives (transitions following a game start, death, or continue) 1 frame faster than Blaster Master (this is likely related to the added continue coding).

Notes
When I first saw the explosion graphic patterns on grenades in MetaFight, I immediately knew the RNG was different.

Credits
ZeroNoin and Skavenger216 each independently found some of the same information here.
Skavenger216 found and was first to mention that items endure resets for reset warps, and lower lag.
ZeroNoin found this same information and other information and was first to share the remaining information.
(I am not sure who was first to mention that there are infinite continues.)
Skavenger216 found that the title screen can lock and not allow Start, and that another reset can fix it.

End