Critical Mass
The turn-based space game where you dragged an arrow from your ship's nose
If you are here because you half-remember a game — Windows, sometime between about 1996 and 2003, top-down, black background, little spaceships, turn-based, and you moved each ship by dragging an arrow out from its nose and then everything moved at once — the game was Critical Mass, by Sean O'Connor. This page is the answer, and the story.
Does this sound like it?
- You commanded a squadron of ships, not one. Several of them, all yours.
- The view was straight down. Space was just black. The ships were small and simple, almost vector graphics — nothing pretty about it, and it did not matter.
- Each turn you dragged an arrow from the front of each ship to set where it would go. You could not turn or speed up as much as you liked — each ship could change its vector by only so much, and that limit was the whole game.
- You picked which missile to fire, pressed a key, and a few seconds passed for everyone at once. Missiles homed on the nearest thing, which was frequently your own wingman.
- When a ship came apart the pilot ejected, and the escape pod was a small circle that could itself be shot at.
- The AI was hard. Not unfair — hard. It weaved out of your line of fire and put missiles on your tail.
- You probably got it from a magazine cover disc, a shareware CD, or a download site with a name like Tucows.
People post this description, almost word for word, on r/tipofmyjoystick every year or two, and it takes a while for somebody to say the name. So, the name: Critical Mass.
What Critical Mass was
Critical Mass is a turn-based space combat game for Windows written by the British programmer Sean O'Connor. You are the commander of a squadron of spaceships sent on one of forty kinds of mission — escort a convoy, attack a starbase, defend Earth — against an enemy squadron flown by the computer. Ships fight with six kinds of missile, all of which home in on the nearest target, so a badly placed shot ends a friend. Ships have shields, and armour, and pilots who can eject.
The turn structure is what made it. You gave every ship its orders while time stood still, then ended the turn, and the whole battle advanced together: your ships, theirs, and every missile in flight. The drag-out-an-arrow control set your heading and how far you would move; a ship's engine put a cap on how much of a change you could make in one turn, so you were always planning two and three turns ahead. It was, in the author's own telling, the biggest and longest project he had built up to that point, and most of the effort went into the AI rather than into the picture — on the reasoning that space is mostly black anyway.
“…more playable than many multi-million dollar productions.” PC Review, January 1996
A short history
| When | What |
|---|---|
| 1988–1993 | A forerunner of the game on the Atari ST, the machine O'Connor wrote his first games for. |
| Early 1996 | Critical Mass for Windows is released as shareware, at the same time as O'Connor's Sound Effects Generator. Reviewed in PC Review (January) and Personal Computer World (February), and carried on magazine cover discs. |
| 1998 | Still being reviewed — Personal Computer World returns to it in November 1998 and calls it hideously addictive. |
| 2001 | Version 3.0: ships that look three-dimensional, better graphics, and a ship and mission designer. If your memory of the game is from around the turn of the millennium, this is the version you played. |
| 2004 | Almost completely rewritten. |
| Today | Still sold and still maintained: a DirectX version for Windows on the Microsoft Store, plus iPhone/iPad, Android and Kindle editions. A free version for Windows is still on the author's site, as it has been since 1996. |
It sat in a family. Sean O'Connor's Windows Games was a one-person shareware label whose other titles — Slay, the hex conquest game that half the internet also half-remembers; Conquest; Firefight; Mother of All Battles; The General — travelled on the same discs, so if two or three of those names ring a bell too, you have the right game.
Where to get Critical Mass
From the author, who is still there:
Critical Mass at Sean O'Connor's Windows Games
That page has the free download, the store links for each platform, a version history, and other people's custom ships. If you played it as a kid and want the feeling back, that is the place — the game is still very much itself.
Why there is a homage
Prisma Duel exists because of the drag. There is a particular feeling to a course you pull out in front of a ship, with momentum you have to plan around instead of a joystick you react with, and nothing else has ever felt quite like it. So the homage keeps that: the overhead view, the secret orders, the simultaneous resolution you sit and watch, and the arrow you drag out of the nose. It changes the rest — one fighter each rather than a squadron, a laser that is a real spectral ray tracer instead of homing missiles, crystals that refract it into a rainbow across the arena, and up to four people in a browser tab, which is not something you could do in 1996.
It is a love letter, not a replacement. How Prisma Duel works explains the rules; games like Critical Mass lists the others in the same family, old and new.
Prisma Duel is an independent tribute. It is not affiliated with, endorsed by or connected to Sean O'Connor or Windows Games Ltd. Critical Mass is his.