Execute this design by thoroughly washing and drying a clear plastic two-liter soda bottle, using scissors to cut the top conical funnel section off four inches below the threaded cap opening. Trim away the threaded pour spout so the bottom opening is wide enough for a marble to pass through without catching. Cut an entry notch in the upper outer lip of the plastic funnel, and glue the end of an incoming paper towel roll track directly into the notch at a tangent angle so the entering marble hugs the outer curved wall. Mount the plastic funnel to your cardboard backboard using hot glue along the rear plastic rim. Position a vertical cardboard drop tube directly beneath the funnel’s lower discharge hole, angling the lower tube to catch the falling marble and launch it into the next horizontal track sequence.
