Sudoku

Beginner
B1  B2  B3  B4  B5  
…
Intermediate
I1  I2  I3 I4  I5 
I6 I7 I8 I9 I10

Advanced
A1  A2  A3  A4  A5
A6 A7 A8 A9 A10

Expert
E1  E2  E3  E4  E5
E6 E7 E8 E9 E10