Logic Masters Deutschland e.V.

❶ The island: The wide grey ring forms a palindrome ring for which the starting point and the two digits in the center of the palindrome share the same number (=X), i.e. XabcdefghXXhgfedcba… The digits a-h does not need to be different

❷ Between lines: value of digit on thin grey line must be between values of digits in the circles at the line ends (r1c2 and r3c8 are connected with a grey line, r1c7 and r2c7 are connected with a black line)

❸ X: The digits 1-9 may appear only once in every row, column, box, and on the diagonals

❹ The less than symbols indicates which cell contains the smaller number

Puzzle: penpa