Traditionally, the last page of Elektor Magazine is reserved for our puzzle with an electronics slant: welcome to Hexadoku! Find the solution in the gray boxes, submit it to us by email, and you automatically enter the prize draw for one of five Elektor book vouchers. Solve Hexadoku and win! Correct solutions received from the entire Elektor readership automatically enter a prize draw for five Elektor Book Vouchers worth $70.00 / £40.00 / €50.00 each, which should encourage all Elektor readers to participate. Participate! Ultimately January 21, 2019, supply your name, street address and the solution (the numbers in the gray boxes) by email to: hexadoku@elektor.com