Light Up is a popular puzzle made by Nikoli
You can play 10 original levels here made by me on a 7x7 grid.
Game engine (code) can support any size of grid.

Place light bulbs (circles) according to the following rules:
Light bulbs are permitted to place at any white squares.
A number indicates how many bulbs are next to it, vertically and horizontally.
Each bulb illuminates from bulb to black square or outer frame in its row and column.
Every white squares must be illuminated and bulbs should not illuminate each other.

Click 'check' to test your progress and find your errors, click 'clear' to clear board.
Click control key any time to reset game and click small arrows to select level.

Problem 1 example: