Puzzles like Sudoku

If you like Sudoku, its closest relatives are Futoshiki, Kropki, Calcudoku and Skyscrapers. You fill a grid so that each number appears once in every row and column, and one extra kind of clue makes each of them its own puzzle. Kakuro, Suguru and Straights keep the digits but change where they may repeat, while Takuzu and Hitori play the same game with two colours or by blacking numbers out. You can play all of them here, free, and every board has exactly one solution.