Marble Run Builder is a free online physics game where you design and build marble tracks from scratch. Place ramps, loops, funnels, bumpers, and trampolines on a grid, then press Test to drop a marble and watch it roll through your creation. The game simulates realistic gravity and momentum so every design produces unique, satisfying results.
Drag track pieces from the bottom toolbar onto the canvas grid. Pieces snap into place and show green when properly connected or red when misaligned. Rotate pieces by tapping or right-clicking. Once your track is ready, hit the Test button to release a marble from the top. The marble follows physics — accelerating on downward slopes, looping through curves, and bouncing off bumpers. Adjust playback speed or replay to fine-tune your design.
In Sandbox mode, you have unlimited pieces and total creative freedom. In Challenge mode, you must guide the marble to a goal zone using a limited set of pieces across 15 increasingly difficult levels.
Marble runs use gravity to propel a marble along a series of connected track pieces. The marble starts at a high point and converts potential energy into kinetic energy as it rolls downhill through ramps, curves, loops, and funnels. Momentum carries it through flat sections and upward curves.
A good marble run balances height changes with interesting features. Start high for maximum energy, use gradual slopes to maintain speed, add loops and curves for visual interest, and ensure smooth connections between pieces. The best runs have a satisfying rhythm of fast and slow sections.
Gravity accelerates the marble at 9.8 m/s² downward. Steeper slopes convert potential energy to kinetic energy faster, making the marble speed up. On upward slopes, gravity decelerates the marble. The total energy is conserved minus friction losses, so height determines maximum possible speed.
Last Updated: March 2026