A marble run is the rare toy that tells a child immediately whether the idea worked. The marble either arrives at the bottom or it stops halfway, and there is no arguing with it. That feedback loop is why a child who will not sit through a puzzle will rebuild a run six times in an afternoon, adjusting one column each go.

PicassoTiles gives 40 pieces to build it with: 18 magnetic squares with an open circle at the centre, 7 quarter round turns, 7 straight slides that double as support columns, 2 long straight slides, 1 short straight slide, 1 U-turn slide, 1 slide and drop combo piece, 1 plain magnetic square and 2 steel weighted marbles. The combo piece is the one that makes the runs interesting, because a marble reaching it can either carry straight on into the next track or turn and drop into a different level of the maze. Pieces run from a 1.38 inch marble to a 6.89 inch long slide, and the square tiles are 2.95 inches, which is the standard PicassoTiles face.

It connects to other full-size PicassoTiles magnetic tile sets, so a marble run can be built through the middle of a tower a child already made. The marbles are steel weighted, which is what gives them the momentum to clear the U-turn. PicassoTiles states the set is BPA free and non toxic with smooth edges on every magnetised tile, and marks its box Ages 3 and up.