ZX84

A ZX Spectrum emulator for your browser & MCP server for AI testing

https://zx84.envytech.workers.dev

Experience the legendary ZX Spectrum with authentic CRT filtering, multi-model support and a powerful integrated debugger. Built from scratch in TypeScript with zero runtime dependencies.

This project has been extensively developed using AI - specifically Claude Code.

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✨ Features

🎮 Complete Spectrum Family

• 48K — The original rubber-key classic
• 128K / +2 — 128KB RAM, AY sound chip, improved BASIC
• +2A / +3 — Built-in disk drive support with full +3DOS emulation

🕹️ Authentic Hardware Emulation

• Z80 CPU — Cycle-accurate with contended memory timing
• ULA — Precise video rendering with floating bus emulation
• AY-3-8912 — 3-channel programmable sound chip (128K models)
• Beeper — 1-bit audio with DC-blocking filter
• uPD765A FDC — Full floppy disk controller (+3 only)

📂 Universal File Support

Load your software instantly with drag-and-drop:

• Snapshots: .sna (48K/128K), .z80 (v1/v2/v3), .szx (ZX-State)
• Tapes: .tap, .tzx with instant ROM-trap loading
• Disks: .dsk for +3 models (standard & extended formats)
• Archives: .zip files with automatic extraction

🎨 Authentic CRT Display

Relive the 80s with customizable visual filters:

• Scanlines — Adjustable horizontal line intensity
• Phosphor Masks — RGB aperture grille or shadow mask patterns
• Curvature — Authentic barrel distortion
• Brightness/Contrast — Fine-tune the picture
• Border Modes — None, standard, or full (for overscan effects)
• Sub-frame Rendering — Pixel-perfect rainbow effects including Nirvana+

🎵 Crystal-Clear Audio

• AudioWorklet — Low-latency, glitch-free sound
• Stereo Modes — ABC, ACB, BAC, or mono mixing
• Volume Control — Individual beeper and AY levels
• Frame Pacing — Audio-buffer-driven timing (no drift)

🕹️ Controller Support

Play your way with multiple input options:

• Keyboard — Full PC keyboard mapping with extended symbols
  • ;, :, ', #, ?, @, ~, {, }, -, +, =, _, [, ]
  • ESC as BREAK (CAPS SHIFT + SPACE)
• Joystick Emulation — Kempston, Cursor, Sinclair IF2, Sinclair 1
• Gamepad — Dual physical controller support via Gamepad API
• Mouse — Kempston mouse and AMX mouse support
• On-screen D-Pad — Touch and mouse controls

🔧 Powerful Debugger

Built-in development tools for reverse engineering and learning:

• Breakpoints — Double-click to set, visual indicators
• Stepping — Step Into, Step Over, Step Out
• Run to Cursor — Right-click any instruction
• Live Disassembly — Real-time Z80 code view at PC
• Register Inspector — All CPU registers with tooltips
• Memory Viewer — Banking state and layout (128K)
• Execution Tracing — Full, Contention, or Port I/O modes
• Loop Detection — Automatic stuck-loop analysis

📊 Activity Monitoring

Watch your Spectrum work in real-time:

• Activity LEDs — Keyboard, Kempston, Tape, Beeper, AY, Disk
• Tape Deck — Block list, position, play/pause control
• Disk Drive — Motor, head, track, sector, operation status
• Performance — T-states/frame, clock speed (MHz)
• Turbo Mode — ~50MHz for fast-loading

💾 Smart Persistence

• Auto-save — ROMs stored in IndexedDB
• Last Session — Restores your last loaded file on startup
• UI State — Model, scale, display settings, pane layout
• Custom Fonts — Load and store .ch8 font files

🎯 Transcription Tools

Extract text and graphics from running programs:

• Pixel OCR — Live character recognition from screen

🔌 Peripherals

Hardware add-ons for expanded capabilities:

• Multiface 1 / 128 / 3 — Snapshot/poke hardware with NMI button
• VTX-5000 — Viewdata/Prestel modem with ROM overlay (48K only)
• +3 Floppy Drive — Motor and seek sound effects

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🚀 Getting Started

Installation

npm install
npm run dev

Open http://localhost:5174 in your browser.

Quick Start

1. Choose a Model — Select 48K, 128K, +2, +2A, or +3 from the hardware pane
2. Load a ROM — Click "Load ROM" and select the appropriate ROM file for your model
3. Load Software — Drag and drop a .sna, .z80, .szx, .tap, .tzx, .dsk, or .zip file onto the window

That's it! For tape files, the emulator will start playback automatically.

Keyboard Controls

• ESC — BREAK (stops tape loading)
• Arrow Keys — Mapped to CAPS SHIFT + 5/6/7/8
• Backspace — DELETE (CAPS SHIFT + 0)
• All symbols — Extended mappings for ;:'"#?@~{}-=_[]

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🎮 Controls

Debugger

• Play/Pause — Run or pause emulation
• Step Into — Execute one instruction (when paused)
• Step Over — Execute, stepping over CALLs (when paused)
• Step Out — Run until RET (when paused)
• Double-click — Toggle breakpoint on disassembly line
• Right-click — Context menu with "Run to here"
• Trace — Select mode (Full, Contention, Port I/O, Loop Analysis)

Display

• Scale — 1x to 4x integer scaling
• Border — None, Standard, or Full
• Scanlines — 0-100% intensity
• Curvature — Off, Low, Medium, High
• Mask Type — None, RGB, Aperture Grille
• Sub-frame — Enable for rainbow/raster effects

Audio

• Volume — 0-100% master volume
• Stereo Mode — ABC, ACB, BAC, Mono

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🏗️ Build for Production

npm run build     # TypeScript check + Vite build → dist/
npm run preview   # Serve production build locally

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📜 License

MIT

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🙏 Acknowledgments

Built with inspiration from the ZX Spectrum community and based on extensive hardware documentation. Special thanks to all the homebrew developers keeping the Spectrum alive!

Enjoy your trip back to 1984! 🎉