Hard. Fill in the grid so that each run of squares adds up to the total in the box above or to the left. Use only numbers 1-9, and never use a number more than once per run (a number may recur in the same row, in a separate run). Printable version at theguardian.com/kakuro A great range of puzzle books is available from Guardian Books. To order, visit guardianbooks.co.uk or call 0330 333 6846.