Update topics

README.md

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 > Brick Breaker is a clone of the classic arcade game Breakout which the player must smash a wall of bricks by deflecting a bouncing ball with a paddle. When all the bricks have been destroyed, the player advances to a new, harder level. The player gets 3 lives to start with; a life is lost if the ball hits the bottom of the screen. If all lives are lost, the game is over.
 
 - **Difficulty**: Beginner
-- **Topics**: Physics
+- **Topics**: Physics, Multiple Levels
 - **Version**: Unity 2019.4 LTS
 - [**Download**](https://github.com/zigurous/unity-brick-breaker-tutorial/archive/refs/heads/main.zip)
 - [**Tutorial Video**](https://www.youtube.com/c/zigurous)