Rules
Light Up is played on a rectangular grid. The grid has both black cells and white cells in it. The objective is to place light bulbs on the grid so that every white square is illuminated. A cell is illuminated by a light bulb if they're in the same row or column, and if there are no black cells between them. Also, no light bulb may illuminate another light bulb.
Some of the black cells have numbers in them. A number in a black cell indicates how many light bulbs share an edge with that cell.
Are you lost? Check out the step by step tutorial

Zooming
Pinch with two fingers to zoom in/out. If you use a mouse you can use the scroll button.

Moving
Tap and drag to move the puzzle. If you use a mouse you can click and drag with the middle (scroll) button.

Marking
You can tap/click individual cell to change its state.

When this mode is selected from the game menu the state of the cell is going from "empty" to "light bulb" to "x" to "empty". If you use the right mouse button the states rotate in the opposite order

If you select one of these modes... Simply put - what you see is what you get.

Check the advanced menu for additional settings and options.