You do not need to know any physics to build your first simulation. You just need to drag, drop, and press Play.
Navigate to /physix/. No account, no install, no download. The simulator loads directly in your browser. You should see a blank canvas with a toolbar on the left and a properties panel on the right.
Click the Circle tool in the toolbar (or press C). Click anywhere on the canvas to place a circle. It appears in grey, waiting — the simulation has not started yet. In the right panel, you can see its default properties: mass = 1 kg, radius = 0.5 m, position, velocity.
In the Environment panel at the top right, enable Global Gravity and set it to 9.81 m/s² downward. This applies gravity to all bodies in the scene.
Click the Surface tool and draw a horizontal line near the bottom of the canvas. This becomes a rigid boundary that bodies bounce off. Set the restitution (bounciness) to 0.7 in its properties.
Click the Play button (or press Space). Your ball falls, accelerates, and bounces off the floor. Each bounce is slightly lower than the last because of the restitution coefficient. Congratulations — that is a working physics simulation.
Add a second ball at a different height. Both fall at the same rate (ignoring air resistance). Add a third ball with mass = 10 kg — notice it falls at exactly the same rate too. Enable air resistance in the Environment panel and place a ball with a very small cross-section alongside one with a large cross-section — now they fall at different rates.
Click the Share button to post your simulation to the Community Gallery. It gets a unique URL you can bookmark or share. Your scenario is stored as JSON — click Export to download a file you can re-import later.
Once you are comfortable with the basics, the Tutorials section walks you through building specific simulations with educational goals — projectile motion, pendulum chaos, solar systems, and more. Each tutorial takes 20–45 minutes and explains the physics alongside the building steps.
Discussion
Questions, corrections, and insights welcome.