Exile

How Exile moves

Mon, 27 Jul 2026 00:00:00 +0000

The previous articles covered how Exile (BBC Micro, 1988) generates its world and draws it. This part is about the thing the game was actually famous for: the physics. Exile’s marketing called it the first game with realistic physics, and for once the marketing undersold the engineering — gravity, momentum, drag, buoyancy, wind, bouncing, all computed for every active object, in 8-bit arithmetic on the same 2MHz 6502 that was also generating the world and drawing the screen.

How Exile draws the world

Wed, 15 Jul 2026 00:00:00 +0000

The previous article looked at how Exile (BBC Micro, 1988) generates its 256×256-tile world from about 500 bytes of code. This one is about what you actually see: how the graphics are stored, how another handful of bytes becomes a red rock face here and a green bush there, and how the sprite plotter gets it all onto the screen fast enough to scroll on a 2MHz 6502.

very piece of art in the game — the player’s spacesuit, thirty-odd creatures, bullets, the spaceship hull, and all 64 landscape tiles lives in one 2,592-byte spritesheet. Add the geometry tables, the tile tables, and the palettes, and Exile’s entire visual identity is about 3.3KB. The rest is, again, technique.

How Exile builds a world

Tue, 14 Jul 2026 00:00:00 +0000

Exile (Superior Software, 1988) gave the BBC Micro something seemingly impossible: a single coherent world of 256×256 tiles with caverns, shafts, diagonal tunnels, a crashed spaceship, an underground base and all on a machine with 32KB of RAM, most of which was screen memory and game code. Stored naively, the map alone would be 64KB. Twice the machine.

The trick is that the map is never stored. Instead there is a function, get_tile(x, y), living at &17b1 in memory, and every time the game needs to know what’s at some coordinate such as for scrolling, for collisions, and for deciding whether a worm can emerge here it calls the function and the answer is computed using a pure function that given the same inputs gives the same answer, every time. The world is a pure function over coordinates, the same insight that let Elite fit eight galaxies into 22KB, here applied not to a star chart but to terrain you can interact with, fly around and collide with, tile by tile. The whole thing is a little over 500 bytes of 6502 code, 54 bytes of lookup tables, and 1KB of hand-placed data for the set-piece locations. Mind boggling frankly.

The source code

Tue, 14 Jul 2026 00:00:00 +0000

There is no source code

Let’s get the awkward part out of the way: the original source to Exile does not exist in any form I have access to. Whatever Peter Irvin and Jeremy Smith’s development setup produced in 1988 — assembler listings, notes, graph paper — is not something you can download.

What you can download is, in some ways, better. At level7.org.uk lives a complete reverse-engineered disassembly of the game, produced without any access to source code, and it is a genuinely heroic piece of work. Every routine named, every table identified, nearly every instruction carrying a comment explaining what it’s doing — around sixteen thousand lines of annotated 6502. The author released it as a tribute to the original developers with no restrictions beyond the game’s own, “in the good faith it was intended”. This project simply would not exist without it.

Why I rebuilt Exile, and how

Tue, 14 Jul 2026 00:00:00 +0000

Why

Exile has been with me for a long time. It was published for the BBC Micro in 1988, written by Peter Irvin and Jeremy Smith, coming towards the end of the BBCs commercial life and when many were, or had, moved on. However it was clear to everyone who played it that it was doing things an 8-bit machine had no business doing: a vast procedurally generated cave system, creatures that seemed to have intentions and certainly showed different behaviours, real physics including gravity, momentum, wind, water and all of it in 32K. It was an open world and a metroidvania before those terms were even coined. And it routinely tops lists of the greatest technical achievements on the platform: it literally seemed like wizardry. It still does.