One Stroke is a drawing puzzle: trace a picture in a single continuous stroke, passing along every line exactly once. Drag from dot to dot, or tap the dots in order. Lifting your finger only pauses; carry on from the glowing dot. If you reach a dot with no untraced line left while lines remain, you are stuck and can try again or undo.
From the second tier, some lines carry arrows and can only be traced the way they point. From the third tier, some lines are double and must be traced twice. Most figures are small pictures, such as a house, a sailboat, a rocket or a turtle. Where you start is nearly the whole puzzle.
Every solution uses the same number of strokes, so stars reward clean solving: finish on your first try with no undo for three stars, and within a few tries and undos for two. The hint puts you on a working start, traces the next line, or steps back to a point from which the figure can still be finished. It caps the level at two stars. Sixty pictures run from Warm-up to Masterpiece, with a daily picture.
Worked example
Take a house: a square with a triangular roof. Count the lines at each dot. The bottom corners have two each and the peak has two, but the top corners of the square have three. When exactly two dots have an odd count, you must start at one and finish at the other. Start at the top left: go up the roof, down to the top right, down the right wall, along the floor, up the left wall, and finish across the top.
Strategy tips
Count first. Odd dots are the only possible starts and finishes.
A double counts twice. It adds two lines at each end, which can change which dots are odd.
Arrows pick the end. An arrow pointing into an odd dot often makes it the finish.