Place every light the level gives you so every thick colored line around the border glows exactly the color it needs, its whole length
Every light has to go somewhere — a puzzle isn't solved until the whole kit is out of the bank, not just enough of it
A level may also hand you a wall to draw yourself — sometimes a goal genuinely can't be lit correctly without it, especially at higher difficulty, but you never have to draw more than the puzzle actually needs
Rules
Each light shines in every direction until it hits an opaque wall edge — the level's own black ones, or one you've drawn yourself
Some lights are already a secondary color (Orange, Green, or Purple) — that light acts as BOTH of its two component colors at once, everywhere it reaches, exactly like a real pair of those two lights overlapping there would
A level can hand you more than one light of the same color, and more than three lights total — extra pieces mean more to place correctly, not an easier puzzle
A goal line only counts as lit once it's completely covered by its color, end to end — a shadow crossing any part of it means it doesn't count
A Red, Yellow, or Blue goal line needs light from only its own color reaching it — any other color landing there too spoils it
An Orange goal line needs both Red and Yellow (and no Blue); Green needs Yellow and Blue (no Red); Purple needs Red and Blue (no Yellow)
Controls
Every light starts parked in the bank below the board — drag one up onto a grid-line intersection to place it (you can't place anything on a wall's own endpoint); same-colored lights share one bank swatch each, with a small number showing how many of that group are still unplaced
Drag a placed light to a different intersection to move it, or back down into the bank to park it again
A wall you're given shows up as its own bar-shaped bank swatch — drag it onto the board and drop it between two adjacent grid-line intersections to draw it there; it BLOCKS light exactly like the level's own black walls, but is drawn white so you can still tell it apart from a generated one
Drag a drawn wall back down to the bank to erase it, or to a different pair of adjacent intersections to move it