Skilled Challenge is a challenge available to test the tile-tapping speed of a player. It is unlocked when the player reaches Level 10. It is located in the Hall.
The application registers the world's best sitting at currently 17.996 tiles per second (as of April 16, 2016). However, many players have claimed to reach score much beyond this score, and these are probably hackers , robots or "slow devices".
There are only 5 songs in Skilled Challenge. The beginning half of Bach's Prelude in E Major BWV 937 plays at the start, with the game starting at 5.00 tiles per second and gradually getting faster and faster. This goes on past the top 50% mark. After ending at the half cadence (with two sets of double tiles nearby), which the speed has increased to 6.55 tiles per second, it transitioned into the second half of Invention No. 13 (also by Bach), and a live blue wallpaper starts to animate in the background, and the stream of tiles continues.
At 8.0 tiles per second, roughly the top 10% mark, the music transitioned into Beethoven's Moonlight Sonata Mvt. 3, and changes the live wallpaper to a pink theme. After a long stream of notes, the 2nd (1-star section) of G minor Bach begins at 9.4 tiles per second. Lastly, at 10.1 tiles per second, which is the top 5% mark, the last section of Fantasie - Impromptu (by Chopin) plays, and ends at 11.2 tiles per second. Completing the Skilled Challenge may be very hard for the player, as the last two songs are only streams of single tiles all the way to 11.2 tiles per second. Some players have gotten so tired at this point they simply fail. The normal current world record is 13.909 by Robio Channel, and 12.256 (with thumbs) by the sister of RandomAir BGM.
The stage then loops back to Prelude in E Major BWV 937.