gpt-oss-20b

A playful 'push and pull' playground for six- to seven-year-olds (grade 1) discovering that a push or a pull can make things move, speed up, slow down, stop, or change direction. A large friendly stage shows one movable object at a time — a toy cart, a ball, or a swing — sitting on the ground. The learner taps a big PUSH or PULL button (or drags the object): a push sends it moving away with a gentle animation, a pull brings it back toward the learner, and a 'how hard' choice (a soft/medium/strong control shown as one, two, or three arrows) makes it move slower or faster and travel a shorter or longer distance. Big friendly arrows show the direction of the force, the object eases to a stop on its own, and a celebratory sparkle plays when it reaches the edge. Design for very young users: oversized tap targets, high-contrast friendly colours on the dark stage, almost no text, and clear cause-and-effect. Controls: PUSH and PULL buttons (or drag), a soft/medium/strong strength picker, an object selector (cart / ball / swing), and a 'Reset' that returns the object to the middle. Acceptance criteria: a push always moves the object in the push direction and a pull moves it toward the learner; a stronger push makes it move faster and farther than a soft one; the direction arrow always matches the actual motion; and 'Reset' returns the object to its starting place.

A 'does it float or sink?' water-tank explorer for grade 2 learners observing that some things float on water and some sink. A large glass tank of water is the stage, with a shelf of everyday objects beside it — a cork, a wooden block, a plastic boat, a leaf and a sponge (floaters) and a coin, an iron nail, a stone and a marble (sinkers). Before dropping an object the learner makes a guess with a FLOAT / SINK toggle; then they drag the object into the tank and it falls with a little splash and settles either bobbing at the surface or resting on the bottom, and the applet celebrates a correct guess and gently corrects a wrong one. A running two-column 'Floats | Sinks' list fills in as objects are tested. Controls: an object picker (or a tray to drag from), the FLOAT/SINK guess toggle, a 'Drop' action (or drag-and-drop), a 'Take out' / 'New set' button, and a 'Reset'. Acceptance criteria: each object always floats or sinks the way it really does; the guess feedback is correct for the object dropped; the water surface shows a small splash and the object settles at the surface or the bottom accordingly; and the 'Floats | Sinks' lists always match what has been tested.

A 'sun and shadows' explorer for grade 3 learners discovering that shadows are made when an opaque object blocks light, and that a shadow's length and direction depend on where the light is. A simple ground scene shows an upright object (a stick, a tree, or a child) casting a shadow on the ground. A big sun moves along an arc across the sky as the learner drags a 'time of day' slider from sunrise through noon to sunset; the shadow swings from one side to the other and grows long near sunrise/sunset and shortest at noon when the sun is highest. A second mode replaces the sun with a torch the learner can drag freely in 2D so they see the shadow always falls on the side opposite the light and gets bigger as the light comes closer. Controls: a 'time of day' slider (sunrise -> noon -> sunset), a Sun / Torch toggle, a draggable light source in torch mode, an object picker (stick / tree / child), and a 'Reset'. Acceptance criteria: the shadow always points to the side opposite the light source; the shadow is shortest when the sun is highest (noon) and longest near sunrise and sunset; moving or removing the light correctly moves, resizes, or removes the shadow; and there is no shadow when there is no light.

A balancing-beam (seesaw) explorer for grade 4 learners building the intuition that a weight tips a balance more when it is placed farther from the pivot. A beam rests on a central pivot with numbered notches (1, 2, 3 ...) marked along each arm. The learner drags weights (1 to 5 units each) onto notches on the left and right; the beam tilts smoothly toward the side with the greater turning effect and sits level only when the two sides balance. For each side the applet shows the simple product weight x distance (as 'blocks x notch') and a little balance meter shows which side is heavier, so the learner discovers that a small weight far out can balance a big weight close in. Controls: a tray of weights to drag on and off, drag-along-the-arm to change a weight's notch, a 'Balance?' check, and a 'Reset' that clears the beam. Acceptance criteria: the beam tilts toward the side with the larger weight x distance and is exactly level when the two sides are equal; each side's weight x distance readout matches the weights and notches actually placed; moving a weight farther from the pivot increases its effect; and the balance meter always agrees with the beam's tilt.

A 'fun with magnets' explorer for grade 5 learners discovering magnetic and non-magnetic materials and that like poles repel while unlike poles attract. A bar magnet with a clearly coloured N pole and S pole sits on a dark stage. In one mode the learner brings the magnet near a row of objects — an iron nail, a steel pin, a paper clip (magnetic) and a plastic scale, a wooden pencil, an eraser and a coin (non-magnetic); magnetic objects jump toward and stick to the magnet while others stay put. In a second mode a second bar magnet appears and, as the learner drags one toward the other, like poles push apart and unlike poles pull together, with a distance-dependent force (stronger when closer) and optional faint field lines shown between the poles. Controls: a mode toggle (test materials / two magnets), an object picker, a 'flip magnet' button that swaps N and S, a distance slider (or free drag), and a 'show field lines' toggle. Acceptance criteria: only the magnetic materials are attracted and the non-magnetic ones are not; two like poles repel and two unlike poles attract; the force is visibly stronger when the magnets are closer and weaker when farther; and flipping a magnet's poles correctly reverses attraction into repulsion.

A simple-circuit builder for grade 6 learners (NCERT 'Electricity and Circuits') meeting the idea that a bulb lights only when it is part of a complete, unbroken loop with a cell, and that some materials conduct while others do not. A board shows a cell (battery), a bulb, a switch, and connecting wires. The learner closes the loop and flips the switch: with a complete circuit the current path lights up and the bulb glows; opening the switch or breaking a wire stops the current and the bulb goes dark. A 'test gap' in the circuit lets the learner drop in different materials — a metal key or coin, a plastic scale, a wooden pencil, a rubber eraser — to see that conductors complete the circuit and light the bulb while insulators leave it off. Controls: an on/off switch, a 'make/break' the loop action, a material picker for the test gap, and a 'Reset'. Acceptance criteria: the bulb lights only when there is a complete loop from the cell through the bulb with the switch closed; an open switch or a broken wire turns the bulb off; conductors placed in the gap light the bulb and insulators do not; and the conducting path is clearly highlighted whenever current flows.

A motion-and-time explorer for grade 7 learners (NCERT 'Motion and Time') connecting speed, distance, and time and reading a distance-time graph. A car (or runner) moves along a straight track at a speed the learner sets, while a distance-time graph draws live beside it: the moving object plots a point each moment so a constant speed traces a straight line whose steepness shows how fast it goes. The learner can add a second, differently coloured mover to compare speeds and see the faster one make a steeper line and reach the end first. A live readout shows speed, elapsed time, and distance (distance = speed x time). A second panel offers a simple pendulum as a timekeeper: a length slider changes how long each swing takes, and the learner counts oscillations against a timer to feel how a pendulum measures equal intervals. Controls: one or two speed sliders, Start / Pause / Reset, a show/hide graph toggle, and a pendulum length slider with an oscillation counter. Acceptance criteria: the plotted distance always equals speed x time and matches the graph and the readout; a faster mover produces a steeper distance-time line and finishes first; constant speed gives a straight line while stopping gives a flat (horizontal) segment; and a longer pendulum has a visibly longer period.

A sound explorer for grade 8 learners (NCERT 'Sound') showing that sound is made by vibrations, that frequency sets pitch, and that amplitude sets loudness. A vibrating source — a plucked string, a tuning fork, or a speaker cone — visibly oscillates on the stage while an oscilloscope panel draws its waveform. A frequency slider makes the source vibrate faster and packs more cycles into the wave, and the applet labels the sound as a higher or lower pitch; an amplitude slider makes the vibration bigger and the wave taller, and labels the sound louder or softer. A live readout shows the frequency in hertz and the qualitative pitch and loudness, and an optional 'play tone' button sounds the note (via the Web Audio API) so the learner hears the change. Controls: a frequency slider (labelled low -> high pitch), an amplitude slider (labelled soft -> loud), a source picker (string / tuning fork / speaker), a Play / Stop tone button, and a 'Reset'. Acceptance criteria: raising the frequency visibly packs more cycles into the waveform and the label reports a higher pitch; raising the amplitude makes the waveform taller and the label reports a louder sound; the drawn vibration of the source stays consistent with the waveform; and at zero amplitude the source is still and silent.

A motion-under-gravity explorer for grade 9 learners (NCERT 'Motion' and 'Gravitation') showing free fall and projectile motion. From a launch pad the learner sets a launch speed and an angle and fires a projectile that follows a parabolic path under gravity; the trajectory is traced, the highest point and the landing range are marked, and a velocity arrow on the projectile updates as it rises and falls. A 'drop / straight up' mode (angle 90 degrees or pure free fall) places markers at equal time steps so the learner sees the spacing grow as the object accelerates downward, illustrating that all objects fall with the same acceleration. A gravity control switches between Earth and the Moon so the learner sees weaker gravity give a longer, higher flight. Live readouts show maximum height, range, and time of flight. Controls: a launch-speed slider, a launch-angle slider (0-90 degrees), a gravity toggle (Earth / Moon) or slider, Launch / Reset, and toggles for the velocity vector and the path trace. Acceptance criteria: the path is parabolic and the range is greatest near a 45-degree launch; a higher launch speed increases the height and range; lower gravity (the Moon) gives a longer time of flight and a higher arc; the equal-time markers in free fall get farther apart as the object speeds up; and the readouts for maximum height, range, and time of flight match the animated motion.

A ray-optics explorer for grade 10 learners (NCERT 'Light: Reflection and Refraction') showing how lenses and mirrors form images. An optical bench has a principal axis, a lens (convex or concave, switchable) or a curved mirror, marked focal points on both sides, and an upright object arrow whose distance from the lens the learner drags along the axis. The applet traces the standard principal rays — the ray parallel to the axis that bends through the focus, the ray through the optical centre that goes straight, and the ray through the focus that emerges parallel — and their intersection locates the tip of the image, which updates live and is labelled real or virtual, upright or inverted, and magnified or diminished as the object moves across the focal points. A focal-length slider reshapes the optics, and a panel shows the lens/mirror formula (1/v - 1/u = 1/f) and the magnification with the current values substituted. Controls: an object-distance slider (or drag), a focal-length slider, a lens-type toggle (convex / concave) with an optional lens<->mirror switch, an object-height slider, and toggles for the ray construction and the formula panel. Acceptance criteria: the principal rays are drawn correctly and meet at the image tip (real images where rays actually cross, virtual images where their backward extensions meet, drawn dashed on the correct side); the image position, size, and orientation always agree with the lens/mirror formula and the magnification; crossing a focal point correctly flips the image between real/virtual and inverted/upright; and changing the focal length or object distance updates the rays and the image consistently.