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Submission #6863: ThunderAxe31's GBC Devil Island "save glitch" in 01:56.08

Console: Game Boy Color
Game name: Devil Island
Game version: any
ROM filename: E Mo Dao (Unlicensed, Chinese) (Multicart Rip).gbc
Branch: save glitch
Emulator: BizHawk 2.5.1
Movie length: 01:56.08
FrameCount: 6943
Re-record count: 1559
Author's real name:
Author's nickname: ThunderAxe31
Submitter: ThunderAxe31
Submitted at: 2020-08-31 00:38:32
Text last edited at: 2020-09-14 09:07:39
Text last edited by: ThunderAxe31
Download: Download (3125 bytes)
Status: judging underway
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Author's comments and explanations:

(Link to video)

Objectives

  • Submitting the first BizHawk 2.5 2.5.1 movie!
  • Saving in a corruptous way!
  • Showing off the GBC BIOS!
  • Shamelessly copying the boss fight from the previous publication, without asking permission to the author!

About the game

E Mo Dao aka 惡魔島 aka Devil Island aka Devil Land aka Alcatraz Island aka Forget Everything You Know About TASing, is a GBC bootleg game by Vast Fame. The game is basically a port of the NES game Getsu Fuuma Den, but with graphics changed in order to make it similar to a Castelvania game. The pseudo-3D levels were omitted entirely. The sound engine is taken from Mega Man V, while the musics are original compositions by Yishen Liao.

Controls

Select button: quick saves the game while on the overworld. Interestingly, there are also save points, but I didn't need these.
Start button: pause the game while in a level. While paused, press A or B to select items for use, then unpause.

Unlock everything fast

In the SRAM, the data about the items unlocked is stored last (SRAM domain, bytes 0x0220-0x0229). So if you turn off the console while saving a new game file, just before the the item data is written, you can have it kept to 0xFF uninitialized bytes, which means that you have all items unlocked, and money and exp maxed. Yay!

Overworld Y buffering

In SRAM memory domain, byte 0x0211 stores the player's X position on the overworld map, byte 0x0212 stores the Y. By resetting at the right moment while saving, we can have the game saving the X position, but not the Y one. This allows for some warping trickeries on the overworld map.

Direction buffering

In SRAM memory domain, byte 0x0213 stores the direction facing. Since the game takes 1 frame when you change direction in the overworld, it's faster to sacrifice some cpu cycles for writing this byte, in some situations. Note that the uninitialized 0xFF byte counts as the direction facing downwards.

Level skip

Discovered by Mothrayas. Save while walking towards a level entrance, and reset the console. After loading the game, you will be standing on top of the level entrance, without actually entering it. From there, you can just walk over it. Note that most levels have two entrances, so you have to do it twice (unless you can exploit the Y buffering trick).

The boss fight

The final boss stage can be accessed only after having unlocked a special weapon, that does require clearing 3 different stages with a boss at the end; it's basically a whip that does project an air blade. This is also the only weapon that can reasonably damage the final boss. I also used the gauntlet, an item that does temporarily double damage dealth to enemies.

Possible improvements

Nope! I dare you try.

Special Thanks

To Mothrayas, for telling me about the level skip glitch, three years ago.

Suggested Screenshot


Memory: Judging

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