The cardboard marble run that took 3 days

I built a marble run out of old delivery boxes. It is taller than my sister.

The plan

I drew it first on paper. The marble starts at the top, goes round a spiral, through a tunnel, over a jump, and lands in a cup.

What went wrong

• Day 1: the spiral was too steep and the marble flew off the track
• Day 2: the tunnel collapsed because I used one layer of cardboard
• Day 3: fixed both, and the jump worked on the first try 🎉

The trick I found

If you fold cardboard into a triangle shape, it gets way stronger than a flat piece. Triangles are the strongest shape. I tested it by putting books on top.