Change difficulty to advanced

Author: adamgraham

README.md

@@ -2,7 +2,7 @@
 
 > Tetris is a tile-matching video game created by Russian software engineer Alexey Pajitnov in 1984. In Tetris, players complete lines by moving differently shaped pieces (tetrominoes), which descend onto the playing field. The completed lines disappear and grant the player points, and the player can proceed to fill the vacated spaces. The game ends when the playing field is filled. The longer the player can delay this inevitable outcome, the higher their score will be.
 
-- **Difficulty**: Intermediate
+- **Difficulty**: Advanced
 - **Topics**: Game Logic, Tilemaps, Grids
 - **Version**: 2020.3 LTS
 - **Author**: [@adamgraham](https://github.com/adamgraham)