Miscellaneous

Things that run in your browser

Small tools, grouped by topic below, almost all of them built with Claude Code; the ideas, the maths and the responsibility for the mistakes are ours. None of them asks you for anything: every "Sign in to continue" on the web costs a little soul, and soul does not grow back.

All tools here run entirely in your browser. Nothing you enter is sent, stored or tracked.

Making Things (7)
  • Terrain Erosion Simulator Simulate hydraulic erosion on a heightmap: rain droplets carve gullies and sediment fans, with live 3D preview and 16 bit PNG export.
  • Heightmap to STL Turn a grayscale heightmap (8 or 16 bit PNG) into watertight STL terrain tiles for 3D printing, with 3D preview and anti-warping options.
  • Trophy Sculptor Set the height, shape a lattice, flame, twisted stele, quartz cluster, bismuth crystals, gnarled tree, power transformer, cup, slit cone, flying wing, F-22, a counterexample lasso or a cube as a graph and engrave the plinth. The STL prints upright without support material, in one colour or two.
  • Sign Maker Build a flat printed sign from parts: a rectangular, oval or cloud-shaped head with raised lettering and frame, on a spike, a band or an octagonal rod for sticking into a cake. Two colours from one filament change.
  • Print Nest Upload an STL and get a transport case that fits it: two halves that close around the model, a cover block or a draped shell, with a set clearance and printable without support.
  • QR Code Generator Free colours, transparent background, PNG and SVG export. The Anatomy view shows which modules carry data and which carry redundancy.
  • PCB Art Designer Turn an image into a light-up PCB: paint with a material palette, then export order-ready Gerber and Excellon files or a KiCad project.
Language Modelling (7)
  • Token & Character Counter Paste text and count tokens, characters, words, sentences, lines and bytes live - with the o200k_base tokenizer (GPT-4o / o-series) and a colored token view.
  • Claude Code settings.json Generator Click together a Claude Code settings.json: permission rules, path rules resolved against the scope you pick, model, environment variables and defaults.
  • System Prompt Builder Click together a personal system prompt for your chatbot: pick a variant per aspect or leave it out, edit any block, copy the result as Markdown - in English or German.
  • Local LLM Frontier What is the best language model your GPU can run? VRAM math for weights and KV cache, honest quality bands and rough speed.
  • LLM Detector Paste English or German text and get a calibrated probability that a language model wrote it, with the typical phrases marked and the driving features shown.
  • Language Zipper Paste a sentence and a character model trained on 87 languages says which one it is, plus a family tree built from how cheaply each explains the others.
  • Text Corruptor Zalgo with a gradient: draw a curve of how corrupted the text gets from first character to last, with fourteen effects landing on whole clauses.
Models & Uncertainty (5)
  • Quap Lab Write a Bayesian model as a formula list, load your data as CSV or JSON and fit it by quadratic approximation or Hamiltonian Monte Carlo. Follows McElreath's Statistical Rethinking.
  • Input Shaping Calculator Driving a damped spring-mass system without residual vibration: ZV/ZVD/ZVDD/EI shapers, step response and sensitivity curve.
  • Drug Concentration Visualiser Pharmacokinetic blood-level curves: drag intake times, combine doses and immediate/extended-release forms, and watch steady-state accumulation.
  • Leverage & Ruin How much leverage is too much? Monte Carlo simulation of a leveraged ETF: volatility drag, the Kelly optimum, break-even leverage and wipe-out probability.
  • Race Time Predictor Enter your running PBs (10K, marathon, …) and get predictions for every other distance - Riegel formula with a personally fitted fatigue exponent.
Playground (6)
  • A Model of PsychohistoryExperimental Posterior predictive futures of a galactic civilization: a coupled stochastic model with priors, interventions and credible bands.
  • Ruler Title Finder You are newly in power and need a title. Seven questions, a transparent fit score, and 44 historical ruler titles with their real history.
  • Grabby Aliens SimulatorExperimental Simulate the grabby aliens model in 3D: expanding civilizations fill the universe and suppress later ones, with honest numbers on how early humanity is.
  • Lambda Diagrams Type a lambda-calculus expression, see it drawn as a Tromp diagram, and watch beta reduction morph it smoothly, step by step. Church numerals, combinators and your own terms.
  • Ripple Tank A live wave simulation, full screen: drop in slits, lenses and prisms or paint walls freehand, and watch diffraction and refraction happen.
  • Reaction Diffusion Two chemicals, four numbers and a full screen. Drag across the feed/kill plane and watch the pattern turn from solitons into worms into dividing cells.
Games (3)
  • Flow Field DefenseExperimental A maze tower defense that draws the field the enemies actually walk on: cost to go, threat coverage and where the crowd will really be.
  • Cobra 6DOFExperimental A wireframe Cobra flown through a gridded box with a 3D mouse, as a real rigid body with its inertia tensor integrated over the mesh. Needs a SpaceNavigator.
  • Asteroid CorridorExperimental A corridor of slowly turning asteroids, flown with a 3D mouse, with no time limit and nothing to reach. Collisions run against the drawn surface, craters and all.
For Parents (8)
  • Name Finder Browse and filter hundreds of German baby names.
  • Parental Leave Planner for Germany (Elterngeld) A grid over 24 life months where both parents assign Basis, ElterngeldPlus or Partnerschaftsbonus, with total payout and a Pareto front of time against cost.
  • Pregnancy Timeline Maps pregnancy symptoms over pregnancy weeks. Also risk curves for miscarriage probability and premature birth survival.
  • Child Development Timeline Visualizes developmental milestones across domains. Overlaid with WHO percentile growth charts for weight and height.
  • Honest Due Date Calculator Models the birth date as a skew-normal distribution with an evidence-based expected due date, based on multiple factors.
  • Birth Decisions ExplorerExperimental Explore the choices around birth: picking an option locks incompatible ones and explains why, with quantified effects and an evidence rating per statement.
  • Infographic: Baby Sleep, Feeding & Crying Total sleep and longest continuous night stretch, feeding frequency (breast vs. formula), and crying and fussing duration per day.
  • Infographic: Daycare Infections Infections per year and sick days per year, shown as P10–P90 bands.
Books (2)
  • Book Recommender Rate the fantasy & sci-fi books you know and get recommendations with calibrated probabilities and a taste map.
  • E-Book Converter Convert EPUB, MOBI, AZW3, Markdown, HTML and plain text into nine formats, one file, a whole batch, or several books merged into one.
Images (9)
  • Background Remover Remove a white or single-coloured background in your browser: flood fill keeps enclosed areas, and an AI mode decides what belongs to the subject.
  • Image Editor Crop, scale, rotate, draw, add text and pull a slanted facade straight, on a non-destructive operation stack you can reorder and roll back.
  • Painting Simulator Paint with pigments instead of pixels: colors mix by Kubelka-Munk optics, so blue and yellow make green, and the brush runs out of paint.
  • Color Extractor Find which colors a photo or logo is really made of and copy them as hex, CSS or JSON: eight palettes from two to nine colors, each with its share.
  • Color Grading Grade a photo in the browser: color wheels, curves, HSL secondaries, split toning and live scopes, plus a tab that develops a Sony ARW raw. Export PNG, JPEG or a .cube LUT.
  • Patch Similarity Explorer Click a spot in an image and see how similar every other region is, from DINOv3 patch features computed in your browser (a 15 MB model, no server).
  • Pixel to Vector Convert a PNG, JPEG or WebP into a clean SVG in your browser: black-and-white tracing with subpixel accuracy, or a color mode with one layer per color.
  • Colormap Designer Build a colormap for the constrained case: colours partly given, or the quantity an angle. A dozen candidates per run, each with its damage report.
  • Pixel Forensics Maps over a photograph that show what the eye does not: the JPEG block grid, the quantisation table the pixels remember, noise and traces of scaling. No verdicts.
Music (4)
  • Choir Part TrainerExperimental Practise your own part from a MusicXML or MIDI score: your voice loud and the rest quiet, slower tempo, transposition, scrolling notation and live pitch feedback.
  • Sheet to MIDIExperimental Upload a PDF of cleanly engraved choir music and get practice MIDI back: music recognition in your browser, per-voice playback, export as MIDI and MusicXML.
  • Sing TrainerExperimental Practice hitting the right notes: scrolling sheet music, live pitch detection from your microphone, generated melodies, scales and hold-the-note drills for every voice type.
  • Vowel Map See which vowel you are singing: the first two formants are estimated live from your microphone by LPC and your voice wanders through the vowel chart.
Everyday (5)
  • Subway Sauce Guide Which sauce goes with which Subway sandwich? Heatmap with switchable color scale.
  • Sun over Regensburg Will the sun still reach this spot at 20:15? Click anywhere on the map of Regensburg and the official surface model answers, buildings and trees included.
  • When to Close the Windows Should you shut the windows the moment it is warmer outside than in? A thermal simulation of every combination of closing and reopening time.
  • Self-Guided Walking Tour (Budapest, Regensburg) A walking tour in the browser, with no app, account or signal: a site plan from OpenStreetMap, a numbered route, and one text per stop. Saves for offline use.
  • German Marginal Tax Wedge How much of the next euro do you keep? Marginal and average burden from taxes, social insurance and benefit withdrawal over the whole income range, broken down by levy.

Tool map: how these tools connect