What is ASTRA — Star Nudging Puzzle
ASTRA gives you one verb. Every orb belongs to a colour, and every colour has a star resting on one of the four sides of the sky. Nudge a star, on the rim or through its chip below the board, and it hops one step clockwise. Every orb of that colour is then pulled towards it and slides until the edge, a rock or another orb stops it. Nothing is ever pushed.
You win when every dashed socket holds an orb of its own colour at the same time. Because one nudge moves a whole colour, and because the star turns before it pulls, the difficulty lies in the order of your moves rather than in your reflexes. Each level carries a par, the shortest solution the game can find, and matching it earns three stars. Later chapters add rock, prisms that repaint an orb, cracked ground that falls away behind you, and voids that swallow whatever slides in.
How to play
- Tap a star on the rim of the board, or its coloured chip underneath; the keys 1 to 4 do the same.
- The star hops one step clockwise, then every orb of that colour slides towards its new side until the edge, a rock or another orb stops it.
- Fill every dashed socket with an orb of its own colour, all at the same time. That completes the sky.
- An orb that slides into a void is lost and the level fails. Undo with Z, restart with R, ask the solver for a colour with H.
Strategies that work
- The arrow on each orb points at the side its star occupies now, but a nudge sends the orbs to the next side clockwise. Turn it a quarter in your head first. Aiming at the side you can see is the commonest wasted move.
- Nothing pushes anything, so other orbs are your only movable walls. When an orb has to stop in open ground, park the blocker first and pull the second orb into it afterwards.
- A socket against the edge in the direction of the pull is free. Any socket further in needs rock, the edge or a parked orb behind it, and finding that stopper is usually the whole puzzle.
- Cracked ground is worth one crossing: it collapses when the orb on it moves away, and the hole is fatal. Hover a star before any pull near a hole, since the ghosts turn red when the move would kill an orb.
- A prism hands its orb to another star. Check where that star stands before you convert, because the orb follows the new colour from then on, and any orb of that colour already in its socket travels with it.
A little history
ASTRA is an original game written for this site, so it has no earlier edition and no inventor to name; its levels were generated and then verified by the solver built into the game. The family it belongs to is far older than any single title: puzzles in which one command moves several pieces at once, each travelling in a straight line until something stops it. Ice floors that refuse to let you stop mid-slide work that way. ASTRA adds two ideas. A move addresses a colour rather than a piece, so one command can carry an orb home and drag another out of place; and a star only ever turns clockwise, which makes direction a resource you spend instead of a free choice. The par above each board comes from a breadth-first search over positions, the standard way to prove that no shorter solution exists.
Frequently asked questions
What happens when an orb falls into the void?
The sky fails at once, because a lost orb can no longer fill its socket. Nothing else is lost: undo steps back one nudge and the orb returns, restart rebuilds the level.
How are the three stars awarded?
Each level carries a par, the shortest solution found by the solver inside the game. Finish in par or under for three stars, up to two moves over par for two, longer for one. Only nudges count, and undo rolls the counter back with the board, so exploring a line costs nothing.
Do I have to finish a chapter before moving on?
Levels open in order inside a chapter, and a chapter opens once about seventy per cent of the previous one is solved, so a stubborn level never blocks the road. Endless mode is open from the start and adds colours, prisms, cracks and voids as your streak grows.
