Solid Line

What it is

Two round characters sit somewhere on a level. You draw lines with a finger, press Go, and the world starts moving. Get the two of them to touch.

Levels in four tiers. Each one gives you a set number of lines (one, two or three), shown as tokens at the top. Undo takes the last line back and gives you the token again.

Along the way come pieces that change what a line can do. Lines stop at the striped zones, though the characters pass straight through them. Pink pads bounce. A character that rolls into one ring comes out of the other, fans blow things along, the red button opens the red door, seesaws tip once something rolls past the middle, and belts carry things the way their arrows point. Keep the characters off the thorns: touching them ends the try. Each piece is shown once, with a one-line hint, the first time you meet it, and most of them arrive in Easy.

Your line stays where you put it

Lines are solid. They do not sag, topple or slide once drawn, which is the single rule the whole game runs on and it takes one sentence to explain.

Nothing moves until you press Go, either. You draw everything first, then watch it play out. That removes the dexterity from it entirely: nothing here is a reflex test, so whoever is standing at the screen starts on equal terms with everyone else.

Every level has been proved solvable

Each level ships with a worked solution, and before it was allowed in, that solution was replayed through the same physics the game uses. Not once, but dozens of ways: at different line spacings, with the points nudged a pixel or two, and snapped to whole pixels the way a real finger arrives on a screen.

A level that only comes out from one exact input is not solvable, it is lucky. Every level passes every one of those runs, every level has then been played to the end in a real browser, and none of them solves itself if you draw nothing at all.

The tiers are measured, not guessed

Difficulty here is measured rather than guessed. Each level is read three ways: how many of five hundred random lines finish it, how far apart the two characters start, and how far one of them has to travel before they meet.

Hard and Expert ask for more than that. Every level there is tried against the straight line a person would draw first, aimed short, true and long, and a level is only allowed in if all of those attempts fail. Each is built around an idea instead: carry one character over a wall, turn it round on a slope, catch both in one line, lob one into a cup, catch a bounce, take one through a hole in a shelf, or roll one into a low tunnel.

No two levels are the same level twice. Each one is compared with every other, and a level that looks too much like one already in is left out.

Easy is picked for variety rather than ease, so it is short, and the first level of every tier is open from the start: you can go straight to Hard if you like.

How to play

• Draw a lineDrag across the level
• Set it runningGo
• Take a line backUndo
• Start the level againRetry

You cannot draw on top of a character or into a striped zone, and lines cannot be added once the run has started. Undo refunds the line, so trying something costs nothing. Within a tier, each level opens when you solve the one before it.

On a desktop, click and drag to draw exactly as a finger does. Nothing is behind a key; the whole game is one gesture. On a wide screen the level fills the height, with the controls in columns either side of it.

What it does not do

No score, no stars, no timer, no lives, no streak, no hints, no ads and no account. A level takes a few seconds to resolve. When the game has the whole screen, as on a kiosk, ninety seconds untouched takes it back to the title and clears the board, so the next person finds a clean level rather than somebody else's half-drawn attempt.

What isn't settled yet

This is the one game here nobody recognizes on sight. Solitaire and mahjong arrive already understood; this one has to be understood in the first three seconds instead, and whether it manages that with nobody explaining is the open question.

Whether there are more levels than the rooms this is built for need, or whether the Expert tier is a tier too far.

Build Log

Credits and licences

Built on matter-js, used under the MIT licence with the licence text reproduced in full in the shipped file. Typefaces are embedded under the SIL Open Font Licence, with their notice retained. Cover drawn from the game’s own level and character code.

Solid Line is original work by Launchway Games.