Analysing the Saturn Loading Screen from the Classic Computer Game: Elite

This paper examines the graphical techniques used to draw the loading screen in the classic 1984 space‑simulation game, Elite, which features a 3D rendering of Saturn, its rings, and a background starfield. Having reverse-engineered the game's 6502 assembler code, we describe how the image is constructed using pseudo‑randomly distributed dots that are selectively filtered to form the planet's disk, its concentric rings, and the surrounding starfield. The most interesting aspect of this code is a single square root operation which we unpack and explain. We reveal that within that operation lies a 3D lighting model of a sphere illuminated from the side, including a texture-mapping effect for the random scattering of pixels that illuminate the planet's surface. This part of the algorithm works by passing uniformly distributed random numbers through an inverse-transform sampling function, such that the output distribution matches the desired lighting intensity with texture mapping. This process produces the illusion of curvature, depth, and directional lighting, despite the absence of conventional polygonal shading. By analysing the algorithmic construction of the Saturn image, this paper highlights how minimal computational resources were used to achieve a visually rich and dramatically anticipatory loading sequence.