OnlyCSharp · built in the open
A workshop of small, dependency-free apps.
Every app here is pure C#, runs offline, and is built on nothing outside the .NET base class library. Some render on the server in about a millisecond; some run entirely in your browser. Pick one and open it.
- Apps live / total
- 45 / 46
- Desktop apps
- 160
- Third-party deps
- 0
- Server binary
- 1.18 MB
- Render
- ~1 ms
Server-rendered opens a razorc page · Runs in browser loads the WebAssembly build · Runs in browser is an interactive JavaScript app · WebGL, desktop needs a graphics-capable browser · Coming soon is built but not yet deployed.
Games
6 appsSolar Sky WalkWalk a real 3D sky rendered from live star and Sun positions.1.8Open PHYSICAA real-physics island you can prod, splash and knock apart.1.8Open SolarWorldA physics-proof sandbox: gravity, orbits and momentum you can check.1.8Open PhysicsOdysseyPlanar mirrors and screen-space reflections in a real-time scene.1.8Open GFX ShowcaseTwenty-one CPU-rendered scenes drawn straight to a canvas.1.8Open Weather ScalesWeather scenes at every scale, from a raindrop to a front.1.8Open
Arcade
4 appsKull ArcadeTwo hundred and ninety-eight Blazor arcade games in one cabinet — pure C#, in your browser.Type oursh to boot a real pure-C# Linux (Alpine) in your browser, on your own CPU.298 games1.4Open JS Arcade — every versionEighty-three arcade classics on one canvas page — plus every historical build preserved and playable.Browse all twelve JS arcade snapshots (best-of, modular, v1.0->v7.5) — latest and historical, each still playable.12 versionsv1.0->v7.5Open GameKit / Cabinet EngineMake your own: the Blazor GameKit / Cabinet engine behind the 298-game arcade, with a 5x7 sprite font.1.4Open Kull.Letters EngineMake your own: the JS Kull.Letters engine behind the 83-game arcade — canvas text-as-graphics 5x7 fonts.v7.5Open
Graphics showcases
7 appsTerminal GraphicsA shaded Utah teapot, a red border and a fisheye magnifier — real terminal graphics, drawn with 24-bit ANSI half-blocks.The exact demo that ran in real Windows and Linux terminals, resurrected in the browser.1.1KullOSOpen Grand Power HallRay-traced industrial physics: water turns a wheel that drives a generator; a boiler powers a steam train.1.7Open Grand Reliquary CathedralA CPU-raytraced stained-glass cathedral board — reflections, refraction and a hero walking all 64 tiles.1.7Open Peril LoopsTwo ray-traced near-escape loops — outrun an avalanche, ride a Gerstner wave — on real physics.1.7Open Drop AtriumSDF stained-glass physics: bodies dropped into an atrium with buoyancy, drag and Magnus lift.1.7Open Mirror LabsFive reflection techniques side by side — Hall-of-Mirrors, Whitted, planar, SSR and SDF.1.7Open GFX BoardsA best-of board: PBR ray tracer, SPH water, Eulerian gas and N-body gravity, all CPU-rendered.1.7Open
Showcases
4 appsCosmos 3DThe flagship: an interactive WebGL solar system, pure C# to the metal. Owns the kull.games root.1.4Open KullOS DesktopA whole desktop in the browser — 160 server-rendered mini-apps across 15 categories.1.61.7Open OnlyCSharp ShowcaseThe live razorc SSR gallery — pure C# rendered to HTML in about a millisecond per hit.1.4Open ObjectKit ViewerAn in-browser 3D model viewer — the first 1.9-era WASM app.1.9Open
Simulations & models
10 appsBridgeCollapseLoad a truss until it buckles, then watch it come down.1.8Open ClimateBalanceA one-dimensional latitudinal energy-balance climate model.1.8Open ColorMapSOMA self-organizing map clustering colours into a living quilt.1.8Open DeltaVPlan an orbital burn and spend your delta-v wisely.1.8Open GridWorldAIQ-learning finds its way across a gridworld, step by step.1.8Open HarvestForecastForecast a crop yield from weather and soil inputs.1.8Open OutbreakLabAn SIR epidemic model you can push past its tipping point.1.8Open PredatorPreyLotka-Volterra population cycles chasing each other.1.8Open SchellingCitySchelling's 1971 segregation model from mild preferences.1.8Open TopoScopeSculpt terrain and read its topology like a scope.1.8Open
Developer tools
11 apps · 10 liveMcAiAsk a math, science, finance or text question in plain English and get an exact computed answer — no LLM.1.71.8Open ImageToolClick a pixel and a pure-C# magic wand selects the whole matching CIELAB colour region.1.8Open FormulaViz182 science and maths formulas rendered as animated GIFs, computed entirely in pure C#.1.8Open
KullEmuA pure-C# x86-64 machine aiming to boot Debian. Research POC.1.8Coming soon
FlightDecodeDecode raw ADS-B flight messages into readable tracks.1.8Open LiveAuthenticatorA live in-browser TOTP / 2FA authenticator, computed in pure C#.1.8Open TerminalQRRender a scannable QR code straight into a terminal.1.8Open TinySQLA SQL parser plus a relational-algebra executor.1.8Open VisionKitFinds the straight lines and circles hidden in an image with classic Hough transforms.1.8Open OnlyCSharpShowcase AppA pre-rendered gallery of ten computed-graphics demos — terrain, star chart, Lorenz, path tracer.1.8Open Authenticator SetupProvision your own 2FA — mint a TOTP secret, scan our own-generated QR into an authenticator app, live-verify.Multi-account, localStorage-persisted, AES-GCM encrypted, zero-server. Our QR is bit-identical to our C# encoder.1.8Open Learning & CS
5 appsPaxosConsensusSingle-decree Paxos with two proposers racing to agree.1.8Open QuantumSearchGrover's search amplifying the answer, amplitude by amplitude.1.8Open SelfPlayChessA real chess engine playing itself to a finish.1.8Open VotingParadoxCondorcet's paradox: majorities that go in circles.1.8Open RetroCoreA tiny retro console core, single-stepping a 6502 in the browser.1.8Open