Yatzy-GB

A version of the dice game Yatzy for the Nintendo Game Boy

Running

A pre-built ROM is available in the tab.

Yatzy-GB has run in all Gameboy/Gameboy Color emulators I've tested as well as on real hardware using flash cartridges. 32KB flash cartridges without an MBC work, though to save highscores a flash cartridge with external RAM is needed - carts with MBC1, 2, 3 and 5 should all work in theory, though I've only tested this 512KB MBC5 cart from insideGadgets.

If you do run into any problems, feel free to make an issue.

Rules & Controls

DPAD - Move the cursor (the > character)

A - Press a button/Score a category/Toggle whether a die is held

B - Return to Menu (from the Game Over screen)

START - Start game (from the Menu)

Yatzy has rules similar to Yacht and Yahtzee. You roll five dice and can then reroll some or all of them twice. To pick which dice to 'hold' on to (ie. not reroll), move the cursor onto the hold button and press the A button to toggle whether to hold the die above the hold cursor (the ^ character) that appears. A star is displayed beneath dice you are holding.

Points are scored by matching different combinations - for instance, picking the 3's category adds the sum of all the dice showing a 3 to your score. You have to use a category once you've used both rerolls and can only use each category once. A star is displayed next to categories you have already scored.

For a full ruleset and complete listing of categories, see the Wikipedia page for Yatzy.

Building

Requires RGBDS to be installed and in your $PATH. Built using v0.5.0 - older versions may work, but I haven't tested them. The provided Makefile works on Linux, though I haven't had the chance to test on either MacOS or Windows.

To build, run make all while in the repository root, the final ROM, yatzy.gb will be in the bin/ directory. make clean will remove the bin/ directory and make run will run the built ROM using an emulator.

The default emulator used by make run is Sameboy, though this can be configured to be any command by changing line 15 in the Makefile or by specifying it in the make command. The path of the ROM will be appended to the command specified. For instance, to copy the built ROM into a different directory, change the value in the Makefile to:

EMU	:= cp -t /path/to/roms

Or by specifying it in the make command:

make run EMU="cp -t /path/to/roms"

Seeding the RNG

By default, the ROM built will seed the RNG used for dice values using the value of DIV register when the player presses start. Alternatively, you can set a constant seed so the same dice are always given in the same order. To do this, set the RNG Makefile variable to a value other than the default of -1. Running make clean will also likely be necessary to force a rebuild:

make clean; make RNG=27659

Credits

inc/hardware.inc

Credit and thanks go to the GBDev community for this file. The original can be found here.

src/core/rand.asm src/core/bcd.asm

Credit and thanks for both of these source files go to Damian Yerrick. I've made no modifications other than to change the file ending from .z80 to .asm. The original files can be found here.

Many thanks to the GBDev community for all the great resources and tutorials.