MOLTEN SPECTRUM

Molten Spectrum is a turn-based puzzle game for the ZX Spectrum 48K/128K. It plays like Sokoban — you push ingots around a grid — but the ingots are metals. Melt them in pots to make alloys, fill the moulds of each order, clean metal in acid, win copper from vitriol, and in the later shops load lasers with metal: every beam carries the colours of its metal, opens spectral doors and melts metal in cold pots.

The old Red Crucible Works is back in business. You are its new smelter: take the orders of fifteen shops, from the casting shop to the spectral lab and the night shifts, and become the master of the crucible.

There is no time limit, no lives and no randomness. Every level was checked by a solver, every move can be undone, and every level has a par — the shortest known solution. Solve a level in par and you earn a MASTER mark.

The game is one tape file, MoltenSpectrum.tap. Open it in any ZX Spectrum emulator (Fuse, Spectaculator, Unreal Speccy, ZEsarUX, Retro Virtual Machine…) or load it on a real machine with LOAD "". The game finds out by itself whether it runs on a 48K or a 128K machine.

After loading, the loading picture stays on the screen while the music plays (128K). Press any key for the title menu.

The goal

A level is solved when every mould holds an ingot of its material and, if the room has spectrometers, every spectrometer is happy.

Moving and pushing

• You walk one cell at a time. Walking into an ingot (or a mirror, or a prism) pushes it one cell — if the cell behind it lets it in.
• You push only one thing at a time and you cannot pull. An ingot pushed into a corner stays there.
• Walls, baths, lasers, spectrometers, shut doors, hot pots and gates against their arrow stop you.
• You may never end a move standing in a beam — such a move is refused (you hear a short burn).

What happens to a pushed ingot

Mirrors and prisms are glass: they cannot go into pots, baths or sockets.

Undo and restart

Every move can be undone (up to 512 moves back) — including melting, dissolving and alloying. There is no way to lose: if a level is stuck, undo or restart it.

Every material is an ingot with its colour and a two-letter label. A beam has the colour of the metal in the laser socket; an alloy shines all the colours of its metals.

The order of the two metals does not matter. An alloy can be melted again and get a third metal: brass + nickel or cupronickel + zinc give nickel silver, steel + nickel gives stainless steel.

Beams

• A laser shines only while an ingot lies in its socket, in the direction away from the socket. The beam has the colours of that ingot: C magenta, Fe yellow, Cu red (warm) and Zn cyan, Sn blue, Ni green (cold). An alloy beam shows stripes of all its colours.
• A beam passes floor, moulds, pots (empty or molten), gates, baths, sockets, cold pots and open doors.
• It is stopped by walls, solid ingots and shut doors. Molten metal lets it through, and so does any metal in a cold pot.
• Beams cross each other freely. After every move all beams are traced again.
• You can never stand in a beam. A beam across a room can cut you off — keep a way round.

Mirrors

A mirror turns a beam by 90°: / sends a beam going right upwards, a beam going up to the right; \ sends a beam going right downwards. Both faces reflect, so one mirror can serve two beams.

The prism

A prism splits a beam by temperature: warm colours (Cu, Fe, C) turn left, cold colours (Zn, Sn, Ni) turn right, as seen along the beam. A bronze beam (Cu + Sn) becomes a red beam to the left and a blue one to the right. A purely warm beam just turns left.

Spectrometers and doors

• A spectrometer adds up all beams that hit it, from any side. It is happy only when it sees exactly its target colours: a missing colour and an extra colour are equally wrong.
• A target can be reached in different ways: a bronze laser, or a copper beam and a tin beam meeting at the spectrometer.
• A spectral door with the same numeral (I or II) is open while its spectrometer is happy, and also while something stands in it: an ingot left in a doorway keeps the door open.

Cold pots

A cold pot is floor in the dark. When a beam (of any colour) falls on it, it becomes a hot pot: what lies in it melts, a second metal alloys with it. Take the light away — pull the ingot out of the laser socket or put an ingot in the beam’s way to cast a shadow — and the metal sets as a solid ingot that you can push out.

Each chapter is a shop of the works with ten orders. Chapters 1–8 teach the machines one by one; from chapter 9 on there are no new machines — only new tricks with the old ones, and the levels become real puzzles. A warning screen opens chapter 9 and an EXTREME! screen opens chapter 14.

• Before the first push, look at every mould and ask: which ingot goes there, and from which side can it be pushed in?
• A pot is a one-way door for metal: what goes in does not come out until it is an alloy. A pure metal left alone in the only pot blocks that pot.
• An alloy is born inside the pot — make sure you can stand on the far side to push it out. A pot by a wall needs a plan for the exit.
• An ingot against a wall can only slide along the wall; an ingot in a corner is lost. Sometimes that is exactly what you want for a spare ingot.
• Not every ingot is needed. Spare metal can be dissolved in acid, parked in a corner, or used as a weight that keeps a door open.
• The ingot in a laser socket is a key: while it shines, the door is open. If the same ingot is needed in a mould, think about when to take it.
• A solid ingot is a shadow. Put one in a beam to cool a cold pot or to close a door behind you.
• Undo is free. Experiment, look, undo.

Names and par (moves) of all 150 levels.

• Written in Z80 assembly (sjasmplus). One tape for both machines: BASIC loader, loading screen, the 128K level bank, the main code.
• On 128K the levels of chapters 9–15 are kept in RAM bank 1; the game detects 128K by itself and falls back to 80 levels on a 48K machine.
• Music: AY-3-8912 (128K, title, chapter screens, finale). Sound effects: beeper, on every machine. A 48K with an AY interface also plays the music.
• Rooms of up to 16×10 cells of 16×16 pixels, smooth movement at 4 pixels per frame, 50 frames per second.
• Every level was solved by a computer solver that follows the game rules exactly; the par values come from it. All 150 levels are replayed move by move in an emulator test against a model of the rules.
• Tested in emulators (48K and 128K). Other models (+2A/+3, Pentagon…) are expected to work but have not been tested on real hardware.

Molten Spectrum — a game by DarkSoL41 (discord: darksol41).

© 2026 DarkSoL41. All rights reserved.