Eleven technical demos. No account, no setup.

Fundamentals of Power Electronics

The step-down converter: its averaged model, and the ripple in its inductor current.

Opens on “Current ripple”

1. Open the demo — it lands on "Current ripple," the University of Siegen's slide rebuilt with live objects.
2. Drag D and watch the ripple and U₂ follow.
3. Step back to "The stationary averaged model" to see the converter solved as a DC circuit, 12 W in and 12 W out.
4. Reset to put D and L back at the lecture's values — nothing you changed is kept.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from “Fundamentals of power electronics” by O. Wallscheid et al., University of Siegen, CC BY 4.0 (doi:10.5281/zenodo.19662909). Modified by Quodra; not affiliated with or endorsed by the university.

Molecular Dynamics Simulations

How a force field turns two numbers per atom pair into motion: the Lennard-Jones potential, and an argon pair simulated with it.

Opens on “Lennard-Jones”

1. Open the demo — it lands on "Lennard-Jones," from the University of Edinburgh's course.
2. Drag σ and the whole well slides; drag ε and only its depth changes.
3. Move to "Force Field Methods" and play the two argon atoms rocking inside the well.
4. Reset to put ε and σ back at argon's values.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from “Introduction to molecular dynamics simulations” by V. Erastova et al., University of Edinburgh, CC BY 4.0 (doi:10.5281/zenodo.17226164). Modified by Quodra; not affiliated with or endorsed by the university.

Basics of Machine Learning: Regularization

Ten noisy points, a degree-9 polynomial, and the penalty that stops it memorising them.

Opens on “Regularizing a Polynomial”

1. Open the demo — it lands on "Regularizing a Polynomial," from RWTH Aachen University's course.
2. Raise log λ and watch the fit stop wiggling, then lose the sine.
3. The fit is computed by the slide's Python cell, in your browser; the first run waits for Python to load.
4. Reset to put λ and the degree back at the lecture's values.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from “Basics of Machine Learning – Regularization” by C. Schmidt and B. Leibe, RWTH Aachen University, CC BY 4.0. Modified by Quodra; not affiliated with or endorsed by the university.

The Central Limit Theorem

Why a sum of coin tosses, standardised, ends up normal — and how fast it gets there.

Opens on “Illustration central limit theorem”

1. Open the demo — it lands on "Illustration central limit theorem," from RWTH Aachen University's course.
2. Drag n up and watch the staircase melt into Φ(t).
3. Move to "How fast the gap closes" for the Berry–Esseen bound against the measured gap.
4. Reset to start the coin again at n = 20 and p = 0.40.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from “Stochastic and Probabilistic Foundations of AI – Central limit theorem” by M. Hirshman and E. Cramer, RWTH Aachen University, CC BY 4.0. Modified by Quodra; not affiliated with or endorsed by the university.

GAMES: Gene Circuit Models

A workflow for building and testing models of synthetic gene circuits, followed on one reference model.

Opens on “Reference model formulation”

1. Open the demo — it lands on "Reference model formulation," from Northwestern University's GAMES lecture.
2. Raise DBD and watch the activation curve move right.
3. Change n to make the promoter more or less switch-like, and read f at kₘ in the panel.
4. Reset to put the promoter back at its reference values.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from the “GAMES” lecture slides by K. E. Dray, Northwestern University (2022), CC BY 4.0 (doi:10.5281/zenodo.7402408). Modified by Quodra; not affiliated with or endorsed by the university.

Waves at Interfaces

Light meeting the boundary between two media: Brewster's angle, total internal reflection, and the power reflection diagram.

Opens on “Power Reflection Diagram”

1. Open the demo — it lands on "Power Reflection Diagram," from Leibniz Universität Hannover's course.
2. Drag θᵢ through Brewster's angle and watch R_TM fall to zero.
3. Swap the media, with n₁ above n₂: a critical angle appears, and past it everything reflects.
4. Reset to put the interface back at air to glass, 40°.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Adapted from “Applied Wave Optics: Waves at Interfaces” by R. Caspary, Leibniz Universität Hannover (2025), CC BY-SA 4.0. Rebuilt as interactive slides by Quodra under the same licence, CC BY-SA 4.0. Not affiliated with or endorsed by the university.

Signal Conditioning

From a sensor's millivolts to a number you can defend — a first-order low-pass filter, live, inside the lecture that derives it.

Opens on “The filter”

1. Open the demo — it lands on "The filter," mid-lecture, already solved.
2. Increase R with C fixed; the cutoff readout falls and the linked resistor value follows it.
3. Move to "The filter response" to see the fixed-baseline sweep a data table drives, independent of the slider.
4. Press Present to walk it full screen, the way it runs in front of a room.
5. Reset to put the filter back at its starting values — nothing you changed is kept.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Acids & Equilibria

From the bond that lets the proton go, to the curve every titration draws.

Opens on “The Proton Handoff”

1. Open the demo — it lands on "The Proton Handoff."
2. Open a molecule in the Studio, add an atom, and come back to the slide.
3. The structure you drew is what the slide now shows — not a picture of it, the structure itself, with its SMILES derived live.
4. Reset to start the molecule fresh.

The task opens the Molecule Studio, a desktop-only gesture; the phone preview still renders the slide and its figure, with no control for this one.

Steel, Heat & Structure

Processing, structure and properties, on one Fe–C diagram you can actually touch.

Opens on “The Fe–C Diagram”

1. Open the demo — it lands on "The Fe–C Diagram."
2. Drag the temperature and watch the state point, the crystal and the pattern move together.
3. Check the diagram's own source and method statement before trusting a region label.
4. Reset to put the alloy back at its starting composition and temperature.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Bend, Bounce & Break

A cantilever's five exams: how far it bends, why its shape matters, how fast it rings, when it breaks, and what it should be made of.

Opens on “How Far It Bends”

1. Open the demo — it lands on "How Far It Bends."
2. Change the section and see stiffness, vibration and failure update.
3. The printed deflection beside the plot is the same number the closed form gives — computed, not sketched.
4. Reset to put the beam back at its starting load and length.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.

Perceptron to Backprop

One neuron, the four points it cannot fix, and the recursion that fixes them.

Opens on “Training XOR”

1. Open the demo — it lands on "Training XOR."
2. Run the trainer and read the loss curve it feeds.
3. Raise the learning rate past the point it thrashes; the failure is part of the lesson.
4. Reset to start the trainer fresh.

Opens with a working touch control on a phone; use a desktop browser for the full editor and Present.