how to play / the physics
A closed reactive molecular-dynamics vessel. Atoms (H, O, C, Na, Cl) move under Lennard-Jones + Coulomb forces (velocity-Verlet). They bond into molecules with correct geometry — water bends (~104.5°), CO₂ is linear (180°) — ionize (Na→Na⁺, Cl→Cl⁻), and merge / decompose. Each cluster is labelled live with its formula + charge as it forms or breaks.
Pick an element (keys 1–5 or the swatches), then tap (or Space) to drop one — it appears where you tap. The vessel starts small and cold; more elements unlock as time goes on (C, then Na, then Cl — the swatches show a countdown). Hold F (or the bottom-left) to heat near your aim — heat drives decomposition and stirs reactions.
Quantum-orbital geometry — press Q to cycle bond rendering: sticks → orbital geometry → blend. Bonds are abstracted to their orbital forms: σ molecular orbitals (bonding density between the nuclei), π orbitals (the side-by-side lobe pair on double bonds), hybrid lone-pair lobes placed in the open VSEPR directions, free-atom s-orbitals, and a hybridisation label (sp / sp² / sp³ from the steric number) on each multi-bonded atom — all derived from the live bond graph. Lobes follow the real cos² angular profile and are phase-coloured (in-phase σ and + lobes blue, − lobes orange — e.g. a π bond shows its opposite-phase pair). The system's definition is preserved (nuclei, formula labels, ledger stay on top). Geometric representation from hybridisation/VSEPR — not a solved wavefunction.
The bond angles are now driven by the orbital geometry: each θ₀ comes from the atom's hybridisation (sp 180°, sp² 120°, sp³ 109.5°) minus VSEPR lone-pair compression (~2.5° per lone pair) — which reproduces water's 104.5° and CO₂'s 180° from the model instead of hardcoding them. (Conservation re-verified: 11.6 ppm.)
Photonic emission — excited atoms (heated by the torch, or fresh from an exothermic reaction — they glow) emit photons that carry energy and momentum, streak across the vessel, and are reabsorbed by other atoms (or reflect off the wall — nothing escapes). Each emission/absorption is a real QED vertex (e⁻ → e⁻ + γ, shown bottom-right); energy and momentum are conserved at the vertex.
Nothing escapes, nothing is created or destroyed. The live ledger (top-left) shows total energy (now including excitation + in-flight photon energy), per-element atom counts, and net charge all staying flat. Try: 2× H near an O → H₂O; C + 2× O → CO₂; Na next to Cl → Na⁺Cl⁻; torch a molecule and watch it radiate.
The ledger now also reports a real temperature (⟨KE⟩) and virial pressure, making it a small MD instrument. There is a convergence certificate (CONVERGENCE.md): this build is "perfect modulo named residuals" — never "perfect." Every conservation claim is checked by headless tests (gentle systems conserve energy to ~22 ppm; under heavy sustained reactive load it relaxes to ~1.5%, a named limit).
Honest model limits — classical molecular mechanics, not quantum chemistry. Valence + reaction triggers are hand-coded rules; bond/ionization energies are tabulated constants. The orbital view is schematic — idealized lobes at classical positions, NOT a solved wavefunction (no Schrödinger/DFT). "Feynman" here = vertex kinematics only — energy+momentum conservation at each emission/absorption vertex is enforced and verified; no QED amplitudes, propagators, or cross-sections are computed. ("Radionics" is pseudoscience and is not simulated — what runs is real radiative photon emission.) 2D ≠ 3D VSEPR; non-relativistic photon E = pc; Coulomb uses 3D 1/r in 2D; reduced units; bounded energy oscillation, not exactly constant. Every conservation claim is checked in headless tests, not just asserted.