/yoshisisland-practice-hack

Practice hack for Yoshi's Island designed to be used on a SNES console

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YI Practice Hack 1.0.1

Practice hack for Yoshi's Island designed to be used on a SNES console

Features:

  • Savestates
  • Re-zone to last room/level
  • Debug Menu
  • HUD
  • Warp to (almost) any room entrance
  • Egg editor
  • Frame advance/slowdown
  • Music on/off toggle
  • Removal of slow score screen and world map animations
  • Enabling built-in Debug functions
  • Button configuration

and more.

Bug reports highly appreciated!

Supports J1.0 and U1.0 versions.

How to patch

Acquire a Yoshi's Island J1.0 and/or U1.0 ROM.

Then, visit https://cbrgray.github.io/yoshisisland-practice-hack to use an online patcher for the latest release.

Alternatively, check the latest Releases for .bps patches, which you can apply to your clean ROMs with a patcher such as flips or beat.

How to use

Debug Menu

To enter menu press Start while holding L & R on controller 1 or just press Start on controller 2. To leave menu press Start on either controller.

Use the d-pad to navigate, B to go back, and Y/A to select options and set values.

HUD

The heads-up display can be toggled on/off from the menu. It may cause some minor graphical glitches and increase lag when enabled. It displays:

Column 1 Column 2 Column 3 Column 4 Column 5
Yoshi's horizontal velocity Red coin amount Stars amount Level timer
Most recent egg-aiming angle Amount of sprites loaded Flowers amount Room timer Input display
Miscellaneous data1 RAM watch2 Slow movement counter3 Lag frame counter

If Yoshi's egg inventory contains a non-standard sprite (either by null egg manipulation, or via the debug menu editor), then the HUD will display different data:

Column 1 Column 2 Column 3 Column 4 Column 5
Yoshi's horizontal velocity Yoshi x position Yoshi x subpixel Level timer
Most recent egg-aiming angle Amount of sprites loaded BG3 vertical offset Room timer Input display
Miscellaneous data1 RAM watch2 Slow movement counter3 Lag frame counter

Note

The HUD data are currently only switched when visiting the world map.

1: The misc. data appear in certain rooms, showing:

  • Prince Froggy's damage value during the fight
  • A trainer for the rockless key clip in 6-6

    • [tongue frame | jump frame | move left frame]

      The values indicate how early or late the input was, with 8 being frame-perfect (e.g. 888)

      • starting from the left corner, begin holding right
      • press tongue after 49 frames
      • press jump after 3 frames
      • stop holding right and start holding left after 6 frames

2: Reads from an arbitrary little-endian address set from the debug menu. The read value appears in the indicated HUD position when the address is set to a value other than $000000.

3: Counts the number of frames that Yoshi spends being slowed while running on slopes, stairs, mud, or snow, or by tonguing, spitting, or swallowing while holding a direction.

Egg Editor

Use A/Y to cycle the sprite in the selected, loaded slot. The previous/next eggs in the cycle are displayed beside the cursor. Current supported sprites:

  • Green/yellow/red/flashing eggs
  • Green/red giant eggs
  • Key
  • NON-STANDARD - boss key (flashing upside-down key), boss explosion, seesaw log, skull mouser
  • Chicken

Savestates

Save your current state while in a level.

Normal (fast) load: works while in the same level as the savestate. Restores changes made to terrain. Certain tiles such as sand may appear visually incorrect, but should still be functional. Full load: re-loads the room, regenerates all terrain. This can be toggled to the opposite in menu.

Loading can be done from anywhere in the same level (but not always guaranteed to work). An after-load delay can be set from the debug menu. The byte value indicates the number of frames the game will be paused for when a savestate is finished loading.

Re-zone

Reset to your last room or level entrance depending on the RE-ZONE LEVEL menu option. Your eggs are saved.

Music Toggle

Enable/disable music (sound effects play as normal).

Free Movement

Enable noclip. Holding A on controller 1 makes you move faster. Yoshi can't collide with terrain in this mode.

File 3 Complete Save

Hold L or R while entering File 3 to enter a fully unlocked save file. Note that the file 3 save can get strange (copy file over and erase it fixes this) Warping before selecting a file will automatically load this save file.

Start-Select to clear a level

Hold L while pressing select in pause menu and you'll leave any level as well as mark it as cleared. This doesn't save until you beat a level legit.

Frame Skip

Increase or decrease frames to skip per frame (amount of slow down). Game will run at 1/n speed where n is slowdown amount. Frame advance mode pauses the game and advances a single frame each time the frame advance input bind is triggered thereafter. It can be disabled via the menu option or by using a bind to change the slow down value. Inputs are buffered in between frames.

Stage Intro (with the level text)

Stage intro will end as soon as the level has finished loading, if there's user input.

Hold any button to load level as fast as possible.

Note

Only applies if the egg inventory doesn't contain a null egg.

Disable Autoscroll

Frees the camera if used during an autoscroller.

Force Hasty

Sets the control scheme to hasty while enabled, otherwise, the controls can be changed in-game as usual.

Soft Reset

Hold L+R+Start+Select on controller 1 for 32 frames to reset the game. This can be useful if you have configured the SD2SNES to load when resetting with the console button, for example.

Button Configuration

Practice functions can be bound to combinations of buttons on both controllers.

  • Press X to remove a binding.
  • Press A to start recording a binding.
  • Once recording begins, press and hold the desired buttons in sequential order, then release them to stop recording.
  • The last button in the sequence is the final trigger, meaning you must hold the other buttons (in any order) and then press the last one to trigger the function.
  • This also means that you should avoid pressing more than one button on a frame when recording.
  • Bindings must be unique for a given function and controller, e.g. you can't bind X on controller 1 to both Save and Load.
  • Note that bindings for controller 2 are recorded using controller 1.

The default bindings are shown below, and may be restored at any time by selecting "reset default":

Controller 1 Controller 2 Function
Select - Save
X - Load
L+X - Load full
R+X - Re-zone
- B Free movement
- L Slowdown decrease
- R Slowdown increase
- A Frame advance
- Y Disable autoscroll

How to assemble manually

First, clone this repo.

This project uses the asar assembler, so download it if you need to.

Run asar.exe assemble.asm path/to/your_rom.sfc from the root directory to apply the patch.

Warning

This will overwrite the clean ROM.

Alternatively, place the clean ROM(s) you wish to patch into the ROMs/ dir (they should be called JP_clean.sfc for J1.0 and NA_clean.sfc for U1.0) then run build.sh or build.bat with no args to build both, or U or J. The build scripts preserve the clean ROMs by copying them before patching.