An illustrative physics playground · Sahilverse

GravityRoom.

Drag, stack and fling objects. Turn gravity up, down or off. Change friction and bounce, then watch what stays the same. A room for asking “what happens if…?” — and checking your guess.

Enter the room ↓ Download the field guide (PDF)

The live simulation needs JavaScript. Everything else on this page — the explanations, the challenge cards, the assumptions and the 16-page PDF field guide — works without it.

The room

Grab an object and throw it. While you hold it, a dotted forecast line shows where it would go if you let go now. Tap empty space to send out a small push.

The interactive room could not start in this browser. The explanations below and the PDF guide describe every experiment.

Presets & challenges Scene

Loads a ready-made scene. Each challenge checks itself and tells you when you succeed.

World rules Gravity 1.00 g

How hard everything is pulled down. 1 g ≈ Earth (9.8 m/s²); 0.17 g ≈ the Moon; 0 = floating.

Floor & contact friction 0.40

How “grippy” touching surfaces are. 0 = ice, 1 = rubber on concrete (roughly).

Bounciness 0.30

How much speed survives a collision. 0 = clay thud, 0.9 = superball.

Mass of new objects 1.0 kg

Heavier objects are harder to speed up — and harder to stop. Size is drawn to match.

Time speed 1.00×

Slow motion or fast-forward. The physics rules don’t change, only how fast you watch them.

Seeing Motion trails

Faint copies show where each object recently was. Spacing = speed.

Velocity arrows

Arrows point where each object is heading; longer = faster.

Depth view (tilt)

Tilts the room in 3D perspective with shadows. Purely visual — the physics stays 2D.

Collision clicks (sound)

Off by default. Soft generated clicks on impacts; louder = harder hit.

Snapshots

Save the whole room — positions, speeds and settings — and jump back later. Stored only in this browser.

Race setup

Top lane mass 1 kg Top lane friction 0.30 Bottom lane mass 5 kg Bottom lane friction 0.30

Both blocks get the same push (6 m/s). Before you launch: predict which stops first. Theory for sliding: distance = v² ÷ (2 × friction × g) — mass isn’t in it.

Race log (this visit)
#	Lane	Mass	Friction	Gravity	Measured	Theory

Every control, in plain language

Grab & fling

Press on an object and drag. It follows your finger like it is on a spring. Let go while moving and it keeps that speed — that’s a throw. The dotted forecast shows its future path under the current gravity.

Tap empty space

Sends a small outward push (an impulse) to anything within about two metres. Close objects get pushed harder; heavy ones barely move.

Pause · Step · Reset

Pause freezes time. Step advances exactly one frame (1/60 s) so you can watch a collision one slice at a time. Reset reloads the current scene.

Zero-g

Switches gravity off and remembers your old setting. Objects keep drifting in straight lines until they hit something — Newton’s first law, made visible.

Snapshots

Three save slots. Saving copies every object and setting; loading restores them exactly, so you can rerun an experiment from an identical start.

Keyboard

Tab into the room, N selects the next object, arrows push it, Space kicks up, P pause, . step, B/O add box/ball, Z zero-g, S/L save/load slot 1, H help.

Readouts

Top-left of the room: elapsed time, object count, total kinetic energy (J) and total momentum magnitude (kg·m/s). Watch momentum stay nearly flat in zero-g.

Focus mode

The button at the top removes decorative motion, trails and the tilt, and enlarges controls. If your device asks for reduced motion, the room starts paused and the landing animation stays still.

Three challenges, reproducible

Challenge 1

Balance a tower

Goal: get a block’s top edge above the dashed line and hold the whole room still for 3 seconds.

Try: wide blocks low, narrow blocks high. Then raise gravity to 2 g and see if your tower still stands — and lower bounciness if it chatters.

Challenge 2

Make an orbit

Goal: fling the small probe so it loops all the way around the heavy core without crashing or escaping.

Try: throw sideways, not at the core. Too slow and it falls in; too fast and it leaves. The forecast line is your best friend.

Challenge 3

Mass vs friction

Goal: predict, then measure, how far two sliding blocks travel.

Try: make one block 10× heavier with equal friction. Then keep masses equal and halve one friction. Which change mattered?

What this simulation is — and isn’t

Gravity Room is an illustrative model, written from scratch for this page. It is good for building intuition and bad for engineering decisions. Here is exactly what it simplifies:

Flat world. Two dimensions only. The depth view is a visual tilt, not a third physical axis.
No rotation. Boxes stay upright and never topple or spin. Real towers fail by tipping; here they fail by sliding or being knocked. This is the biggest simplification.
Simple contacts. Collisions use instant impulses with one bounciness value and Coulomb-style friction (friction force capped at μ × normal push). Static and sliding friction are the same number.
Fixed time slices. The room advances in 1/240 s substeps using semi-implicit Euler integration. Energy can creep slightly up or down; very fast objects can occasionally pass through thin gaps.
Orbit core is a cartoon star. The orbit challenge uses an inverse-square pull that is softened near the centre so nothing divides by zero. Orbits are “orbit-like”, not astronomy.
No air. No drag, no wind, no spin — unless you count the small damping applied to keep stacks from jittering forever.
Units are nominal. The room is 16 m × 10 m by definition. A “kilogram” here is a number in the model, not a measurement.

The PDF guide explains each of these in more depth, with experiments that deliberately expose them.

Free download · 16 pages · PDF

Physics for Curious Creators

A field guide for people who learn by poking things: plain-language explanations of gravity, mass, impulse, friction, bounce, momentum and orbits; a predict–test–explain loop; ten experiments you can run in this room; printable challenge cards; a chapter on what this model gets wrong; and real references for going further.

Download the PDF guide

No sign-up. The file is bundled with this site and downloads directly from it.

Explore related worlds

Other Sahilverse experiments that share a question with this room. Each link below was checked and loaded on 25 October 2026.

World Engine

Rules make worlds

Gravity Room asks what happens when you change one rule of a physical world. The World Engine asks the same of a body of ideas — a navigable galaxy where projects become stars and you collide two of them on purpose.

Visit worldengine.sahiltayal.com ↗ SYNAPSE

Systems you can manipulate

Here, forces combine into motion. In SYNAPSE, two ideas are blended in a “synthesis reactor” and drawn as physics-inspired generative art. Same spirit: transparent rules, visible outcomes, no hidden AI.

Visit synth.sahiltayal.com ↗ The atlas

Back to the Sahilverse

The home of every experiment, essay and side quest: psychology, education, perfumery and many more playable questions. Gravity Room is one door among many.

Return to sahiltayal.com ↗

Privacy, plainly

No accounts, cookies, analytics, ads or trackers. The page makes no network requests beyond loading its own files. Snapshots and your Focus-mode choice are saved in this browser’s local storage and never leave your device; clear them with the “Forget everything” button below or your browser settings. Sound is off until you turn it on.