Introduction

This book teaches Glimmer, a reactive language for Z80 games. You describe a game as its state, its inputs and the rules that react to them, writing the behaviour itself in small blocks of assembly; the compiler generates the frame loop, input polling, change tracking and display support around your declarations. We build the model one construct at a time, and by the final chapters the pieces combine into Canvas, a complete interactive program with structured state, multiple source files and cards.

The language

A Z80 game written by hand spends most of its code on plumbing: the loop that runs every frame, the polling that notices a keypress, the bookkeeping that knows which parts of the display changed. Glimmer moves that plumbing into the compiler. Your source declares facts and the rules that respond when they change, and each rule's body is a short piece of assembly doing exactly one job. The generated program is readable AZM source — the plumbing is code you can open, not a runtime you must trust.

This book teaches Glimmer 0.6, and every complete program in it is built with glimmer build, so each chapter's result runs.

The intended reader

We assume you can read simple Z80 assembly — loads, jumps, comparisons — because rule bodies are written in it. AZM Book 2 teaches those fundamentals from nothing if you need them first. No experience with reactive programming is assumed; the model is taught here from its first construct, and readers who know reactive frameworks from larger platforms will find the ideas familiar and the costs far more visible.

The book's method

Each chapter adds one construct and builds something with it. We begin with the shape of a game and a first light on the display, then take state, pulses and bindings, and the compute–effect–render cycle in turn. The middle chapters add the 8x8 matrix profile, time, motion curves, shapes and sound; the later ones bring arrays and layout types, the dependency reports that make a reactive program debuggable, routines and imports for larger sources, and finally cards. Exercises appear throughout, with notes at the end.

When the model is complete, Glimmer Book 2 applies it to three full games — Skyfall, Tetro and Rushlight — across two display systems. The reference appendices hold the declaration tables, display profiles and build commands for lookup.

The first chapter draws the shape all these games share.