KAZA.cz / recomp

Recompiled Spectrum Classics

Original ZX Spectrum games, translated instruction by instruction from Z80 machine code into JavaScript – no emulator inside. The game logic is the original one, cycle for cycle; everything around it is new: smooth HD picture without colour clash, steady speed, touch controls and full screen.

Perfectly smooth scrolling in the old classics – just the way you remember it. Every game can switch live to the classic mode, which turns all the enhancements off.

Play now

Teenage Mutant Hero Turtles – loading screen

Teenage Mutant Hero Turtles

1990 · Image Works / Probe Software · action platformer

Leo, Raph, Mike and Don in the sewers and streets of New York – switch turtles, ride the party wagon, save April.

  • Hand-tuned turtle sprites with coloured bandanas, bricks in shadows
  • Saved games: 3 slots, download & upload
  • Infinite lives, invincibility, double time for the underwater bombs

© 1990 Image Works / Mirrorsoft Ltd., under licence from © 1989 Konami and Mirage Studios, USA. Teenage Mutant Hero Turtles™ is a trademark of Mirage Studios, USA. ZX Spectrum version by David Perry & Nick Bruty (Probe Software).

Nebulus – loading screen

Nebulus

1987 · Hewson · rotating-tower platformer

Guide Pogo up eight towers rising from the sea – ledges, doors, lifts and nasty creatures – before the time runs out.

  • Smooth rotation of the tower at your monitor’s refresh rate, bricks drawn in HD
  • Pogo and the creatures redrawn as smooth curves, constant speed, saved games
  • Improved controls: a separate Jump key and touch button, ↑ jumps where there is no door or lift, Ctrl only shoots
  • Start at any tower, infinite lives, invincibility, time speed 0× / 0.5× / original

Nebulus © 1987 Hewson Consultants Ltd. Written by John M. Phillips.

H.A.T.E. – loading screen

H.A.T.E.

1989 · Vortex Software / Gremlin Graphics · isometric shoot’em up

Hostile All Terrain Encounter: fly the fighter and drive the tank through ten isometric zones, collect pods, shoot everything.

  • Smooth scrolling at your monitor’s refresh rate, interpolated sprites and shadows
  • Constant speed – no slowdown with many objects
  • Autofire, infinite lives, invincibility

© 1989 Vortex Software, published by Gremlin Graphics. Written by Costa Panayi, music by Ben Daglish.

Abu Simbel Profanation – loading screen

Abu Simbel Profanation

1985 · Dinamic Software · flip-screen platformer

Johnny Jones, cursed by the pharaoh, explores the temple of Abu Simbel – 45 deadly rooms, a diamond of the right colour for every door, jumps measured to the pixel.

  • Smooth motion at your monitor’s refresh rate, no attribute clash: Johnny and the creatures keep their colours
  • Johnny and the creatures redrawn as smooth curves, constant speed, saved games
  • Arrow keys + Ctrl and a touch controller with long and short jump
  • Infinite lives, invincibility

Abu Simbel Profanation © 1985 Dinamic Software. Program by Víctor Ruiz, with Florentino Pertejo, Santiago Morga B. and Snatcho.

Jetpac – loading screen

Jetpac

1983 · Ultimate Play The Game · shoot’em up

Jetman assembles his rocket, fuels it with six pods and blasts off to the next planet, while eight kinds of aliens swarm in – Ultimate’s very first game.

  • Smooth motion at your monitor’s refresh rate, no attribute clash: every alien keeps its own colour
  • Jetman, the aliens and the rocket redrawn as smooth curves; constant speed – no slowdown when the screen is full
  • Arrow keys + Ctrl (↓ hovers), touch controller with Fire, Thrust and Hover; start at level 1, 5, 9 or 13
  • Autofire, infinite lives, invincibility, saved games

Jetpac © 1983 A.C.G. – Ultimate Play The Game. Written by Tim and Chris Stamper.

PSSST – loading screen

PSSST

1983 · Ultimate Play The Game · arcade

Robbie the robot guards his prize plant from slugs, leeches and midges – each bug falls only to the right one of three spray cans, the wrong one just stuns it.

  • Smooth motion at your monitor’s refresh rate – even the bugs’ step-and-pause crawl glides; no attribute clash on the plant, its leaves or the bugs
  • Robbie, the bugs, leaves and flowers redrawn as smooth curves; constant speed – no slowdown in a full swarm
  • Arrow keys + Ctrl, touch controller with Spray and Pause; start at plant 1, 2, 3, 4 or 7
  • Infinite lives, invincibility, a plant that never wilts, any spray kills, saved games

PSSST © 1983 A.C.G. – Ultimate Play The Game. Written by Tim and Chris Stamper.

Video Pool – a moment of play

Video Pool

1984 · Oxford Computer Publishing · pool

Pot the six numbered balls before your shots run out – three game variations, small or large pockets, two players and a table editor for trick shots.

  • The balls roll at your monitor’s refresh rate on their exact sub-pixel paths; no flicker where they overlap
  • Balls redrawn as smooth circles; constant speed – no slowdown in the break
  • Aim with a tap or click on the table, arrow keys + Ctrl, touch controller with Shoot; start at frame 1, 3, 6 or 10
  • Infinite lives, unlimited shots, aim help (the line of the shot), saved games

Video Pool © 1984 Oxford Computer Publishing Ltd (OCP). Written by James Hutchby.

Extreme – the loading screen

Extreme

1991 · Digital Integration · scrolling shoot’em up

An alien ship has crash-landed on Earth and its self-destruct is counting down: fly through it with your jet pack, pick up the weapons and objects its crew left behind and disarm it in time.

  • The game moved its window by whole characters 13 times a second – now the scenery, the hero and the creatures glide smoothly at your monitor’s refresh rate, the stars in two parallax layers
  • No attribute clash: the scenery keeps its colours under the sprites; hero and creatures redrawn as smooth curves
  • Constant speed – no slowdown when a lot is going on; arrows + Ctrl with any control, touch controller with Fire and Weapon
  • Infinite energy, shields and ammo, the countdown at 0× or 0.5×, saved games

Extreme © 1991 Digital Integration Ltd. Original program and design by Dave Perry and Nick Bruty.

Double Dash – the loading screen

Double Dash

1990 · VooDoo · two-player cave digging

Two moles dig through 24 caves together: collect the diamonds, dodge falling boulders, skulls and butterflies and get out through the flashing exit – side by side on one keyboard or over the internet.

  • Network game: one player starts a server, the other connects with a code – both see the same game, each in his own browser
  • Single player mode with the whole picture for one mole; a map of the whole cave; restart the cave or respawn with a button
  • The views crawled 8 pixels a move after the moles – now each view sweeps to its mole in two seconds and glides with him, always in the middle of the picture
  • Moles, boulders, diamonds and creatures slide smoothly from cell to cell instead of jumping, redrawn as smooth curves
  • AY music and sound, a dead mole comes back (in the original he waits for the other one), start in any cave A–X, infinite lives, invincibility, time 0× / 0.5×, saved games

Double Dash © 1990 VooDoo. Written by Tomáš Pártl and František Fuka.

SQ-Demo – a frame of the demo

SQ-Demo

1994 · Depeche Code · AY music demo

A Czech music demo for the 128K’s AY sound chip: eleven SQ-Tracker songs, the letters of the logo jumping to the beat, volume bars and a scroller.

  • The AY-3-8912 sound chip emulated, in ABC stereo or mono
  • Smooth scroller and jumping letters at your monitor’s refresh rate; the flickering volume columns steady, the flashing background cross-faded; logo letters redrawn as smooth curves
  • Previous / next song at once (arrow keys or touch buttons), pause, start at any of the 11 songs

SQ-Demo © 1994 George K. of Depeche Code. Music: Kyrril / George K., Qjeta, Scalex, Betabyte.

What’s new in the old games

✨

HD smooth picture

4× resolution, motion interpolated between the game’s frames at your display’s refresh rate. Optional edge smoothing (Scale2x).

🎨

No colour clash

Sprites keep their own colours instead of the Spectrum’s two colours per 8×8 block. Classic mode is one click away.

⏱

Steady speed

No slowdown when the screen gets busy. Speed slider 0.5–2×, or type any value.

🕹

Controls for everyone

Arrows + Ctrl work in every control mode the game offers. Draggable on-screen controller on phones and tablets.

⛶

Full screen

Only the game picture, landscape on phones; swipe anywhere to steer, tap to fire.

💾

Settings remembered

Cheats, speed and graphics are kept in your browser. Infinite lives and invincibility when you just want to explore.

🖥

Windows app

One small .exe with the game inside: own window, no address bar, offline. Uses the Edge engine already in Windows.

▶

Straight into the game

“Just into the game!” skips the title screens and menus – or start with the intro for the full experience.

How it’s made

  1. Disassembly. The tape image is traced and turned into commented Z80 source that reassembles byte for byte into the original.
  2. Recompilation. Every basic block becomes a JavaScript function with exact T-state timing; self-modifying code reads its operands from memory.
  3. Verification. Recorded runs are replayed against a reference Z80 simulation and compared register by register and page by page.
  4. New renderer. The game’s own drawing is captured and redrawn in HD – the logic never notices.
// Teenage Mutant Hero Turtles, main loop - recompiled
function L923C() {  // $923C
  a = m[0xED62]; t += 13;            // LD A,($ED62)
  cp8(0x19); t += 7;                 // CP $19
  t += 7; if (f & 0x40) { t += 5; return 0x9247; }  // JR Z,$9247
  cp8(0x0E); t += 7;                 // CP $0E
  t += 7; if (!(f & 0x40)) { t += 5; return 0x92BB; } // JR NZ,$92BB
  return 0x9247;
}