Tetris (Game Boy)

Tetris
Developer: Nintendo R&D1 Publishers: Nintendo, Hyundai (KR) Platform: Game Boy Released in JP: June 14, 1989 Released in US: August 1989 Released in EU: September 28, 1990 Released in KR: 1990 This game has unused code. This game has unused sounds. This game has revisional differences. This game has a Data Crystal page

The Game Boy Tetris is a very famous rendition and the system's pack-in game for American consumers. The game was so popular, it led to the Game Boy being a major success for Nintendo.

Unused Jingle

An unused level-up sound, present only in Version 1.0. Game Genie code 084-F5D-E62 will replace the existing sound upon leveling up.

(Source: nensondubois)

Revisional Differences

Version 1.0 was only released in Japan as part of a Special Link Bundle, and is estimated to have sold around 25,000 copies. Version 1.1, used for the rest of the Japanese print run and released internationally, contains the more widely-recognized A-TYPE music and is overall a slightly more polished game.

Copyright Screen

v1.0	v1.1

Hyphens were added between "Bullet" and "Proof". Also, the copyright screen is displayed for just two seconds in v1.0; this was extended for v1.1 to eight seconds, although pressing Start after four seconds will take you to the title screen.

Music and Sounds

v1.0	v1.1

The A-TYPE song in v1.0 is Minuet. v1.1 replaced it with Korobeiniki, which had previously been used in BPS' Famicom version and has since essentially become the Tetris theme.

v1.0	v1.1

The "level-up" sound was changed from a simple beep to a short jingle.

Level 9

Version 1.0 requires you to score 20 lines on Level 9 to proceed to Level 10. This was changed for v1.1 to 100 lines, much like most other versions of the game. This was presumably done as if the player started gameplay on Level 9, they would reach Level 10 as soon as they scored only 20 lines.

Block Rotation Glitch

Version 1.0 lets you rotate a block while clearing a line, multiple lines, or a Tetris if there is room in the playing field.

Input During Line Clears

As with the block rotation, v1.0 also reads the directional input during the line clear delay. This allows you to "charge" the Delayed Auto Shift, which makes the next block start to auto-shift in the direction held immediately after spawning. This is very handy during higher levels. This also allows the player to trigger a minor sound glitch, by playing the short beep in response to the movement input and cutting off the much longer line clear sound effect.

v1.1 doesn't read directional input during the line clear delay, so there's still a pause before the next block starts auto-shifting, and no sound glitches can be triggered this way.

Unused Code

Demo Recording

There are leftover facilities to record demos like the ones that are shown after one sits on the title screen for some time. Recording is active if memory address 0xFFE9 contains 0xFF.

This condition cannot be met by normal means, as the code that activates recording is not reachable unless one patches out an early "return" instruction in the initialization routine.

When recording is enabled, you would wait for the demos to start. The game won't play any stored movements, but allows you to control the game instead. The recorder captures the current input on every frame and stores it to the address specified by 0xFFEB and 0xFFEC. They point to ROM locations per default. Developers would have had to extract them using a debugger or change the location to point to SRAM or other writable media.

For each game mode, 0x100 bytes worth of inputs are stored before the next mode starts. To save some space, especially during idle frames, the game compresses inputs using run-length encoding.