← Back to the gamebug or idea?Terrapin Trail//Code BibleIIhow the game works, archive to van

A guided read of one small, complete game

Learn a whole codebase,
one file at a time.

Terrapin Trail is a comedic Oregon Trail-style RPG about following a band on tour. The game itself is about 3,900 lines of hand-written JavaScript in a single file; around it, a small Python server turns the Internet Archive's Live Music Archive into playable tours with shared, tagged leaderboards. Chapters 0–12 read the game; 11 and 13–18 cover the server, the archive, sharing, rules, fair play and hosting. Every code excerpt is read live from the code that is running.

Two ways in — same 19 chapters, pick your level

Field Manualfor people who already codeFast and dense. Quotes the source directly, points at exact lines, names the gotchas. Start here if function and state are old friends.Open the Field Manual →First Tournew to codeTeaches every idea from scratch — variable, function, loop, server, test — using the game as the example. No experience assumed.Start the First Tour →

The setlist

00Foreword: how to read this01The philosophy: one file, no build02Anatomy of one file03The state machine04Data-driven design05The game loop & a leg06The crew system07Taping the show08Economy, buffs & caps09The Peak, scoring & endgame10Persistence11The server12Determinism & testing13The Live Music Archive pipeline14Tags, links and where players came from15Game DNA: rules as data16Fair play and shared luck17The page around the game18Running on Vercel

Also inside

Q&A index238 searchable questions, each answer linked to the source line.Function mapThe load-bearing functions, each linking into the code.Further readingThe companion player wiki and where the raw files live.