Make a road from the start to the goal
・You cannot cross dragon squares.
・You must cross all squares once except dragon squares.
・You can cross either vertically or horizontally.
・You cannot cross diagonally.
Fill the grid with number 1 to 4
・Every row and every colum must have every disit between 1 to 4.
・Digit within each heavily outlined group of squares indicates the sum of the numbers in that group.
for more training: KENKEN (external link)