(TAS) - The Tower of Druaga (1984) Any% [HP underflow exploit]

[This TAS but the lights are on:    • (TAS) - The Tower of Druaga (1984) Any% [H...  ] [If you'd like more granular TAS info about this game, here's another TAS I made with commentary:    • (TAS) - The Tower of Druaga (1984) Darknes...  ] Hi, so this is a tool-assisted speedrun of the 1984 Japan-only arcade game The Tower of Druaga. The exploit I use to cheese the final boss in this TAS, however, is not possible in the original arcade version, so I am instead playing the PSX port included in Namco Museum Vol. 3 from 1997. Having spent a considerable amount of time digging into the code of the PSX version, as well as starting a TAS of the arcade version, I am confident in saying the human play experience of this port is very faithful to the arcade game. Minor differences exist with the way level and enemy info is cleared from memory during transitions, and the coordinate grid has a different origin in each version (PSX - origin is top left, increasing right and down; Arcade - origin is top right, increasing left and down). When the player hitbox contacts that of an enemy that deals damage but does not instakill (knights, lizardmen, ropers, and dragons), the player's HP decreases by 1-2 (depending on the enemy) on each frame of contact. The HP underflow exploit comes into play when taking damage from two enemies at the same time. The player should die when HP falls to zero, but what happens when HP hits zero AND decreases on the same frame? The unsigned byte flips from 0 to 255 and wow infinite health amazingggggg!!! [Technically, you could do this in real time, if you get lucky. Basically a coinflip.] The PSX-exclusive trick for the final boss Druaga is a little different. The game checks explicitly for certain inventory items (full set of Hyper Armor, Excalibur, and Blue Crystal Rod) whenever the player touches Druaga. If any item is missing, HP is set to zero and it's game over, man (literally, the game becomes unwinnable, even if you have extra lives), but the player's HP can still decrease below zero on that frame from another enemy, so HP is continually set to 255. In the original arcade game, maybe this interaction happens in the other order or something different is done to resolve the conflict, but extra damage does not override Druaga's instakill... ㅠ ㅠ [No way you could do this in real time. Good luck not accidentally killing the second enemy.] Anyway, exploit #1 is used on Floors 57 and 59, and exploit #2 is used on Floor 59. This is also a low-ish% run. At an absolute minimum humans could win with 27 items collected, while a "dev-intended path" TAS would need 22. This TAS collects only 8 to go fast. Theoretically, this could be TAS'd with only 1 item (the Ruby Mace required to defeat the dragon on Floor 59) but it would be soooo slooooooowwwwww. Bizhawk 2.11.1