High speed decision making required. Drag and drop the towers to their own color. The towers grow as long as the color matches. Mismatches let them shrink.
When one tower grows above a stage line you reach the next level. When three towers shrink so much that they disappear - you lose the game.
The difficulty is pretty high by default. The background colors change frequently so that you have to adjust the tower positioning. The multiplicator is based on the level, the amount of growing towers and your lifes. Losing one tower (and one life) decreases the multiplier enormously.
Short beginners guide:
1. Focus on the shortest tower and try to keep all towers alive by that strategy.
2. When you start feeling comfortable, focus on the shortest and highest tower. Then you have a good chance to reach a high score.
3. After some training your concentration should be good enough to focus on more than two things at once.
Good luck and enjoy the game!