Light Up is a puzzle game that I enjoy playing. You have to place lights in a grid of squares so that all squares all illuminated while no lights light eachother up. Squares with numbers on them must have that many lights as neightbors.
Click here to try the game out yourself
Here are some tips I can give your after playing for a while:
The most basic example I can give is this:
The only way to light up the bottom left square is to put a light there.
Take a look at this image:
Look at that 3. That number cannot have a light both above and to the left of it because then we wouldn't be able to put another light next to the 2. That means those 2 squares must only have 1 light in total. Because of that, we can place a light under and to the right of the 3.