Coleco TennisNES Port

The 1989 Game Boy Tennis, ported to the ColecoVision.\r\n\r\nNintendo\'s classic Tennis now runs on a 32K ColecoVision cartridge. You play a full match against the computer, with four difficulty levels and 1 or 3 sets. Mario is in the umpire\'s chair.\r\n\r\nThe game logic is not a remake: it is the original Game Boy code, translated instruction by instruction to the ColecoVision\'s Z80. Ball physics, shot angles, the CPU player\'s behaviour and the scoring rules are all the Game Boy\'s own.\r\n\r\nFeatures\r\nThe full Game Boy stadium, 256 pixels wide, fills the screen.\r\nThe original four shades of green are kept.\r\nThe players are drawn with hardware sprites: red for you, blue for the CPU.\r\n4 difficulty levels, and matches of 1 or 3 sets.\r\nTwo control modes:\r\n2 buttons (default): left fire to hit, right fire to lob;\r\n1 button: either button hits, and the game lobs automatically when your opponent comes to the net.\r\nSound effects on the SN76489 sound chip.\r\nThe game runs at 60 frames per second.\r\nControls\r\nAction ColecoVision controller\r\nMove Joystick\r\nHit Left fire\r\nLob Right fire (2-button mode)\r\nMenu: choose line / change value Joystick up/down / left/right\r\nMenu: level Keypad 1-4\r\nStart the match Any fire button\r\nHow to play\r\nDownload tennis.rom and load it in a ColecoVision emulator, such as openMSX, blueMSX or ColEm. The emulator needs the ColecoVision BIOS, which is not included. You can also run it on real hardware with a flash cartridge.\r\n\r\nMade for real hardware\r\nThe ColecoVision\'s video chip, the TMS9918A, is strict: if video memory is written too fast while the screen is being drawn, the data is silently lost on a real console. Coleco Tennis only writes video memory in two situations:\r\n\r\nwhile the screen is off, to draw the title and the court;\r\nduring the vertical blank, from data prepared in RAM.\r\nEvery video access was checked in a cycle-counting simulator: none is too fast, and the vertical-blank update uses about 60% of the time available.\r\n\r\nMade with AI\r\nThis port was made with Claude, Anthropic\'s AI assistant, working together with a human developer.\r\n\r\nClaude did the technical work:\r\n\r\nreverse-engineered the Game Boy ROM;\r\nwrote a translator that converts the Game Boy\'s SM83 code to Z80;\r\nmoved the game\'s memory into the ColecoVision\'s 1 KB of RAM;\r\nwrote the display, sound and controller code in assembly;\r\nbuilt the graphics converters and the simulator that checks the timing rules.\r\nThe translated game logic was checked step by step against the real Game Boy game running in an emulator: over 2,700 game steps, the ball, players and score match exactly. The only differences come from one deliberate tweak that makes the player\'s angled shots slightly shorter.\r\n\r\nThe human developer directed the project, tested the game and decided how it should look and play.\r\n\r\nColeco Tennis is part of a series of ports of the same game, all made the same way: ZX Spectrum, Commodore 64, Amstrad CPC and CPC Plus/GX4000.\r\n\r\nCredits\r\nOriginal game: Tennis © 1989 Nintendo. This is an unofficial, non-commercial fan port, not affiliated with or endorsed by Nintendo.\r\nPort: made with Claude (Anthropic).\r\nTools: sjasmplus, SkoolKit, PyBoy, openMSX.