Practice
Champion technique
Simple Colouring
Chain a digit through every unit where it fits just two cells, and colour the chain in turns. One colour holds the digit. A cell that sees both colours can't hold it, and a colour that meets itself in a unit is the false one.
1FocusOnly what mattersNext
Start2Notes givenFull grid, notes filled inLocked
3Your own notesFull grid, you make the notesLocked
4Against the clockHow many in a row?Locked
5 right in a row passes a level