Eulero ©
Rules
Fill each cell of the grid with one number from 1 to 5 and one letter from A to E (size 4x4: 1 to 4 and A to D, size 7x7: 1 to 7 and A to G) such that no number and no letter appears twice per row or column, and that each combination of a number and a letter appears exactly once in the whole grid.
Sample puzzles
EASY
MEDIUM
HARD
EVIL
All puzzles © by puzzlephil