Cardboard Marble Run

Cardboard tubes — collect paper towel rolls and toilet paper rolls (6-10 is a good number)

A large piece of flat cardboard, or prop a cardboard box open

Masking tape or painter's tape

Scissors (adult help for cutting)

Marbles or small bouncy balls

A cup or container at the bottom to catch marbles

Start by cutting some tubes in half lengthwise to make open channels. Keep some tubes whole for tunnels. You'll want a mix of both.

Lean your large cardboard piece against a wall at an angle, or use the inside of an open cardboard box as your building surface.

Tape the first tube near the top of the cardboard. Angle it slightly downward so a marble will roll through it.

Place the second tube below and slightly to the side, so the marble drops from the first tube into the second.

Keep adding tubes, alternating between half-tubes (open channels you can see) and whole tubes (tunnels).

Place a cup at the very bottom to catch the marble.

Test with a marble after every 2-3 tubes. Adjust angles and positions until the marble rolls all the way through.

Add a funnel at the top by cutting a tube at an angle to create a wide opening.

Create a jump by leaving a small gap between two tubes — the marble will fly through the air.

Make a spiral by curling a long strip of cardboard around a tube.

Add a ramp at the bottom that launches the marble into the cup.

Try racing two marbles side by side with parallel tracks.

Gravity pulls the marble down, but you control the path it takes. Every tube has to be angled correctly or the marble gets stuck.

When something doesn't work, that's the most important part. Ask: "Why did the marble stop there? What can we change?" This is how real engineers think.

Challenge your kid: "Can you make the marble take at least 10 seconds to reach the bottom?" Longer runs are harder because every connection has to work.

Start small. Build a 3-tube run first, get it working, then add to it. Trying to build the whole thing at once leads to frustration.

Masking tape is better than clear tape because it's easy to peel off and re-stick when you need to adjust angles. You'll be adjusting a lot.

If you don't have cardboard tubes, cut paper plates in half and fold them into channels. Pool noodles cut in half work great too.

This is a true STEM activity. Your child is practicing engineering (building structures), physics (gravity, momentum, angles), and problem-solving (debugging when the marble gets stuck).

Save the marble run! If it's built on a box, you can keep it and add to it over several days. Kids love coming back to improve their design.

For an extra challenge, try different sized balls. A ping pong ball behaves differently than a heavy marble — it's lighter and bounces more.