Connect at least 3 similar letters. Merge them into the next alphabet letter. Keep merging until you get to Z.
Press the left mouse button to start. Now move the mouse on identical adjacent letters (horizontally, vertically or diagonally). Select at least 3 letters. Release mouse button to let the match happen. This will merge the selected alphabet letters into the next letter of the alphabet.
For example, if you select 3 or more blocks labelled with `A`, the resulting letter will be the `B`. Keep matching and merging the letters until you get the `Z`.
In easy mode you can upgrade to higher letters easily, whereas in normal and hard mode upgrading takes more work.