Labs
Interactive simulations and visual explainers — play with physics, algorithms and AI in your browser.
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Physics Simulations
11 pages-
Cloth Simulator
Drag, cut, pin and tear a cloth of points and springs with Verlet physics, wind and a ball. Free online cloth sandbox with six presets.
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Double Pendulum
Free double pendulum simulator: drag the bobs, trace the path and watch chaos grow with up to 200 pendulums, an energy readout and a phase plot.
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Electric Field
Free electric field simulator: drag point charges to see field lines, equipotentials and a potential map, read E and V anywhere and release a test charge.
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Falling Sand
Pour sand, water, oil, lava, fire, ice, plants and acid into a free falling sand sandbox and watch them flow, burn, melt and react. No download.
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Fluid Simulator
Stir real-time 2D smoke and ink in your browser. Paint walls, place jets, tune viscosity and swirl, and watch a Navier–Stokes solver at work.
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Gravity Simulator
Launch planets and moons, build star systems and watch orbits form in a free N-body gravity sandbox with presets, trails, zoom and energy tracking.
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Ideal Gas
Ideal gas simulator: move the piston, heat or cool bouncing particles and watch pressure, volume and temperature obey pV = NkT on a live p–V diagram.
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Physics Sandbox
Free 2D physics sandbox: stack boxes, throw balls and link shapes with pins, rods, ropes and springs. Change gravity, friction and bounce, then blow it up.
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Projectile Motion
Launch a projectile at any angle, speed and height. Compare throws on Earth, the Moon or Mars, add air resistance and wind, and aim at targets.
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Ray Optics
Trace light rays through lenses, mirrors, a prism and a glass block. See real and virtual images, Snell's law, total internal reflection and dispersion.
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Wave Simulator
A virtual ripple tank: watch 2D waves interfere, diffract through slits, reflect off walls and refract in a slow medium. Draw your own sources and walls.
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Life & Emergence
4 pages-
Epidemic Simulator
Watch a fictional infection spread through moving dots and test distancing, vaccination and quarantine with live charts. Free epidemic simulator.
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Flocking Simulator
Watch boids flock with separation, alignment and cohesion. Tune the rules, scare the flock with a predator, add obstacles and try up to 1,500 birds.
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Game of Life
Play Conway's Game of Life online: draw cells, place gliders, guns and oscillators, try rules like HighLife and import or export RLE patterns.
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Particle Life
Watch life-like clusters, chasers and cells emerge from simple attraction and repulsion rules. Edit the rule matrix, share seeds and try up to 4,000 particles.
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AI & Algorithms
6 pages-
Digit Recognizer
Draw a digit and a small neural network reads it. See every neuron and weight, edit them by hand, or teach a fresh network your own symbols.
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Genetic Algorithm
Watch rockets evolve to reach a target. Tune selection, crossover and mutation, draw obstacles and see the DNA of every generation. Free and in your browser.
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Logic Gate Simulator
Build digital circuits from AND, OR, NOT, NAND, NOR and XOR gates, flip the switches and watch the wires, lamps and truth table update live.
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Neural Network Playground
Watch a small neural network learn to separate two classes of points, see every weight and change any of them by hand. Free, runs in your browser.
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Pathfinding Visualizer
Draw walls and mud on a grid and watch A*, Dijkstra, BFS, DFS and greedy search find a path step by step. Compare them, tweak heuristics, build mazes.
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Sorting Algorithm Visualizer
Watch bubble, selection, insertion, shell, merge, quick and heap sort animate step by step with live counters, pseudocode and a side-by-side compare mode.
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Sound & Music
13 pages-
Chladni Patterns
Sweep the frequency of a vibrating plate and watch thousands of sand grains settle on the nodal lines. Chladni figures with sound, right in your browser.
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Doppler Effect
See and hear the Doppler effect: a moving sound source, exact wavefronts, a draggable listener, pitch readouts, a frequency graph and the Mach cone.
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Drum Machine
Free online drum machine: a 16-step sequencer with eight synthesized drums, swing, three kits, preset beats, finger pads, WAV export and share links.
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Lissajous Figures
Free Lissajous figure generator: set the frequency ratio and phase, hear the two tones in stereo and watch musical intervals draw closed curves.
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Music Sequencer
Free online music sequencer: draw a melody, bass, chords and drums on a step grid, lock notes to a scale, then export a WAV or share a link.
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Noise Generator
Free noise generator: play white, pink, brown, blue, violet and green noise, shape it with filters and watch its live spectrum and slope in dB per octave.
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Sound Picture
Turn a picture into sound and watch a spectrogram draw it again. Play it, save it as WAV, or send it through the air to another device's microphone.
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Sound Visualizer
See sound live from your microphone, your computer's audio output or a file: oscilloscope, spectrum analyzer, spectrogram and pitch detector.
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Standing Waves
See and hear standing waves on a string and in open or closed pipes: pick harmonics, mix modes, add two travelling waves and sweep through resonance.
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Synthesizer
Play a polyphonic synth, bass line sequencer, drawbar organ, plucked string or FM synth, and see how oscillators, filters and envelopes build each sound.
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Theremin
Play a free online theremin with mouse, finger or keyboard: slide for pitch and volume, add vibrato, snap to a scale and replay your own phrase.
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Tone Generator
Free online tone generator: play pure tones from 1 Hz to 22 kHz, sweeps and beats, see period, wavelength and note, and try a hearing-range experiment.
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Tuning Systems
Hear and see how equal temperament, just intonation and Pythagorean tuning differ: play intervals and chords, compare cents and watch beats appear and vanish.
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Hearing & Perception
9 pages-
Auditory Illusions
Hear six classic auditory illusions in your browser: Shepard tone, tritone paradox, missing fundamental, binaural beats, octave and continuity illusion.
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Auditory Masking Demo
Hide a tone in noise and hear it return. Explore critical bands and the upward spread of masking, then measure your own masking curve at 1 kHz.
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Equal-Loudness Contours
Measure your own equal-loudness contour with headphones: match tones from 63 Hz to 12.5 kHz to a 1 kHz reference and compare the curve with ISO 226.
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Headphone & Speaker Test
Free online headphone and speaker test: check left and right channels, polarity, centre balance, frequency range, driver matching and rattles.
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Hearing Loss Simulator
Free hearing loss simulator: play music, speech-like sounds or your own audio through an audiogram and switch between normal and simulated hearing.
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Hearing Test
Free online hearing test for headphones: find the quietest tone each ear can hear from 125 Hz to 16 kHz and watch your audiogram build up. Not a medical test.
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Pitch Discrimination Test
Free pitch discrimination test: hear two tones, say if the second is higher or lower, and find your smallest detectable pitch difference in cents and Hz.
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Sound Localization Test
Free sound localization test for headphones: explore time and level differences between your ears, then measure the smallest ones you can hear.
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Tinnitus Matcher
Find the tone or hiss closest to your tinnitus: match its pitch and loudness with headphones, check the octave and save the result. Not a medical test.
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Radio & Signals
7 pages-
Signal Identifier
Find out what an unknown radio signal is: the page listens, analyses it step by step and names Morse, RTTY, PSK31, SSTV, fax and more, with the decoder to open.
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DCF77 Decoder
Decode the DCF77 time signal from your receiver's audio in the browser: time, date, all 59 bits and parity checks, plus a guide to receiving 77.5 kHz.
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Morse Decoder
Decode Morse code (CW) from your receiver's audio in the browser: automatic tone and speed, noise rejection, waterfall tuning and a practice sender.
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PSK31 Decoder
Decode PSK31 and BPSK63 radio text from computer audio, a microphone or a recording, with a waterfall, automatic tuning, a phase scope and a demo signal.
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RTTY Decoder
Decode RTTY (radioteletype) from your receiver's audio in the browser: waterfall, auto-tune and AFC, 45.45 to 100 baud, 170 to 850 Hz shift.
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SSTV Decoder
Decode slow-scan television pictures from radio audio in your browser: Martin, Scottie, Robot and PD modes, automatic start, slant correction and a demo.
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Weather Fax Decoder
Decode shortwave weather fax (radiofax) charts from your receiver's audio in the browser, with automatic start, phasing, slant correction and PNG export.
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Maths
6 pages-
Fourier Drawing
Draw any shape and watch a chain of rotating circles redraw it with the Fourier series. Then build square and saw waves from sine waves and hear them.
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Fractal Explorer
Explore the Mandelbrot set and its Julia sets: zoom to the limit of double precision, trace orbits, switch palettes and formulas, and save PNG images.
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Galton Board
Free Galton board simulator: drop balls through 1 to 20 rows of pegs, change the left/right odds and watch the binomial and normal distribution appear.
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Matrix Transformations
Drag the basis vectors of a 2×2 matrix and watch the plane transform: determinant, inverse, eigenvectors and matrix multiplication made visible.
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Spiral Gears
Free online gear drawing toy: roll a toothed wheel inside or outside a ring, pick the pen hole and layer colourful rosettes. See why petals equal N over gcd.
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Strange Attractors
Rotate the Lorenz attractor and five other chaotic systems in 3D, change their parameters and measure the butterfly effect with a live growth-rate chart.
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