Light Loop: a loop puzzle through every bulb
Lay one closed loop of wire through every bulb on the board. Holes and walls leave exactly one way to do it. Close the loop and the whole string lights up, starting from the plug.
How to play
Your first puzzle is a four-spot practice square. You can wire two separate pairs, then join the pieces into a single loop. Start with any ring. Choose your puzzle after that. The ? button lets you replay the lesson.
- Drag between bulbs to lay wire. Wire runs up, down, left or right, never diagonally. Start anywhere: the corners are usually the easiest place.
- Every bulb takes exactly two wires. One in, one out. Dark gaps have no bulb, and the wire cannot cross a wall.
- Include the plug in your loop. Connect two wires to the lightning bolt, just like a bulb. When one loop runs through the plug and every bulb, the string lights up from the plug.
Drag over wire you have laid to lift it, or tap a bulb to clear both its wires. Undo and Restart are free, and there is no clock. Daily gives everyone the same single board for the date. Unlimited deals one board at a time. Choose Another puzzle when you want a new one.
Where to start
A corner bulb has only two neighbours, so both of its wires are already decided. The same goes for any bulb squeezed between a wall, a gap and the edge. Lay those first, then look for bulbs that now have only two ways left.
Choose Hint to see one connection and the reason it matters. You draw or erase it yourself. Watch for small loops: closing a ring before every bulb is on it can never be the answer, so the board will not let you.
Questions
Is there always exactly one answer?
Yes. Every board is checked when it is made: there is one loop that passes every bulb, and each wall on the board is needed to rule out the others.
Can I play with a keyboard?
Yes. Focus the board, move with the arrow keys, and hold Shift with an arrow to lay or lift wire in that direction. Space clears the bulb you are on, Backspace undoes and R restarts.
Is there a daily puzzle?
Yes. Everyone gets the same 6×6 puzzle each day. Your wire stays in this browser when you come back. Choose Unlimited for more boards and harder puzzles.