Paul Withers

Atari Lynx projects

Independent work in C and 65C02 assembly

Independent development for the Atari Lynx, a 1989 handheld console. Embedded programming in C and 65C02 assembly against 64 KB of RAM and the Suzy sprite-scaling hardware.

Wolfenstein 3D Complete

A conversion of the 1994 Macintosh first-person shooter to a handheld console from 1989 with 64 KB of RAM. Built from the original Mac source code, the whole game fits on a 512 KB cartridge, and has been developed over five years. Every wall is drawn as a single Suzy hardware-scaled sprite, keeping rendering cost on the CPU close to zero. The game is played with the Lynx held in portrait orientation (TATE mode).

SpecificationMacintosh (1994)Atari Lynx (1989)
CPUMotorola 68020 or later65C02, 4 MHz
RAM4 MB64 KB
Display640 × 480160 × 102
Colours on screen25616
StorageHard disk512 KB cartridge

The full version, shown above, is complete but not publicly released. The shareware release (the first three levels) is available to download.

Download the shareware on AtariAge

Screenshots

Wolfenstein 3D title screen on the Atari Lynx
Title screen
Wolfenstein 3D main menu on the Atari Lynx
Main menu
Scenario select screen listing the six episodes
Scenario select
Three guards in a stone corridor, viewed in portrait TATE mode
Guards
A sliding steel door opening onto a guard
Doors
A room with treasure, a table and red banners
Treasure room
Fighting Hans Grösse, the episode one boss
Hans Grösse
Fighting Hitler, the episode three boss
Hitler

How a frame is drawn

Animation of a Wolfenstein 3D frame being built up one sprite at a time
One frame built up sprite by sprite, in portrait orientation.
Ten steps showing walls and enemies drawn in BSP order
Walls are drawn in BSP order, one Suzy sprite per wall segment. This entire view takes six sprites.
Diagram of Suzy stretching and tilting a sprite into a perspective wall
Suzy can stretch each scan line of a sprite and shift where each line starts. Combined, the two give a perspective warp at almost no CPU cost. It only reads as perspective from the side, so the game is played in portrait (TATE) mode.

Suzy also multiplies and divides in hardware while the CPU carries on with other work. Scheduling the perspective maths so the CPU and Suzy run in parallel was the most time-consuming optimisation, and the most effective.

Art conversion

Original PC enemy sprites beside their Atari Lynx conversions
The enemy cast: original art (left) and Lynx versions (right). Every asset was reduced to a custom 16-colour palette, resized, then touched up by hand.
Original PC wall textures beside their Atari Lynx conversions
Wall textures, original and Lynx. 245 KB of art packs into 81 KB on the cartridge, and only about 5 KB is in RAM at any time.

Development tools

Custom Wolfenstein 3D map editor
Map editor, written in Python.
Custom Lynx sprite editor showing an SS guard
Sprite editor for the Lynx art, written in Python.
GearLynx emulator running the game with profiling panels open
A modified GearLynx emulator with added profiling tools for CPU and sprite-engine timings.

Other projects

Super Mario Bros. on the Atari Lynx
Super Mario Bros. Released
A complete port of the NES original. Source code is public; building it requires a legally owned NES ROM.
github.com/pwsqrd/lynx_smb
Prince of Persia on the Atari Lynx
Prince of Persia In progress
A port of the Atari ST version, including its full set of rotoscoped animation frames.
Lester in his lab from the Another World intro, on the Atari Lynx
Another World In progress
A port of Éric Chahi's polygon-based game, rendered with Suzy's hardware drawing.
Animated Mortal Kombat II fighters on the Atari Lynx
Mortal Kombat II Prototype
Technical prototype: converted sprites and a background demonstrating large fighters, move sets and a two-player ComLynx link mode.
Ryu and E. Honda on Ryu's stage, reduced to the Lynx palette
Street Fighter II′ In progress
A conversion of the PC Engine Champion Edition. The game code is being converted to 65C02 and its graphics redrawn through Suzy. Shown: a palette and layout test.
A Wizard of Wor dungeon with Burwor monsters and the radar, on the Atari Lynx
Wizard of Wor In progress
A port built from a disassembly of the Commodore 64 version.