Turn a collection of cardboard tubes into an open-ended construction project with a fun payoff.
Cover the tubes with colored tape. Use a craft knife (a parent's job) to make half-pipe tubes and window cutouts as shown, if you like.
Place self-adhesive magnet strips on one side of the tubes and attach them to the refrigerator.
Let your kids assemble — and reassemble — the run with the tissue box at the bottom on the floor to catch the speeding marbles.