Because

A standalone editor and renderer for MindMup argument visualizations (.mup files). MindMup discontinued free argument-visualization access through Google Drive in June 2026; Because runs the same MIT-licensed rendering engine (mindmup/mapjs) with the product's own argument-mapping theme, so existing course maps open unchanged and render the way they did in MindMup. (Briefly named ArgumentBase — legacy infrastructure IDs such as the Firebase site argumentbase keep the old name.)

Run it

Hosted: https://app.philmaps.com (also at argumentbase.web.app, the underlying Firebase site; deployed from this repo with ./deploy.sh). Locally, no build step is needed — the engine bundles are committed:

python3 -m http.server 8871      # from the repo root
open http://127.0.0.1:8871/app/

• Drag any .mup file onto the window to open it, or use File → Open.
• File → Save writes a standard .mup (JSON) that MindMup-family tools read.
• Google Drive open/save is built in (drive.file scope, Picker-based); enabling it on a deployment takes one OAuth client — see docs/drive-setup.md.
• Microsoft OneDrive open/save is built in too (Graph Files.ReadWrite, PKCE popup auth, in-app picker); enabling it takes one Entra app registration — see docs/onedrive-setup.md.
• Work is autosaved to the browser's localStorage as crash recovery; the status text tracks whether the map is saved to its file.

Keyboard (the philmaps.com set)

Press ? in the map for the full reference, which renders its keys for either platform (⌘/⌥ or Ctrl/Alt) and detects which one you are on. The keys below are written Mac-first; on Windows and Linux read ⌘ as Ctrl and ⌥ as Alt.

Key	Action
Enter	add reason under selected claim
Tab	add co-premise to selected claim
Alt+O	add objection
Alt+Q	add neutral connector — only while View > Allow neutral connectors is on
T (or Alt+T)	toggle reason/objection (on a bracket) or implicit/explicit (on a claim)
Alt+N	add sticky note
D	detach the selection — a claim, or a whole reason / objection — from the tree
L	label the connector above the selection
arrows	navigate; Shift+arrows select several claims at once
⌘←/→	reorder a claim among its co-premises
F2 / Space	edit; F collapses the branch; Delete removes the selection
⌘Z / ⌘⇧Z	undo / redo (Ctrl+Y also redoes on Windows)
Z / Shift+Z	zoom
Shift+T	dark / light mode
Escape	leave the map — focus moves to the menus, since Tab inside the map adds a co-premise
?	the keyboard reference

app/js/shortcut-help.js holds the table the reference renders, and the features e2e cross-checks it against shortcuts.js, so a binding added without a line in the reference fails the suite.

The argument-visualization grammar

• Co-premises (claims that jointly make one reason) share one bracket with a single stem; independent reasons get separate brackets with fanning stems.
• Green rounded brackets support; red square brackets are objections.
• Blue flat brackets are neutral — an uninterpreted connector that asserts no relation, so a question can carry the claims that answer it, or a claim the question it raises. Switch it on under View > Allow neutral connectors; it is off by default, and with it off there is no neutral tool in the toolbars and no Alt+Q. Maps that already use it always render it, whichever way the preference is set. The three bracket kinds differ in shape as well as colour.
• Dashed borders mark implicit claims; sticky notes are yellow handwriting notes; claim numbering (1.1, 2.1 …) is a view toggle. Click a number to put your own text there instead (up to 10 characters, stored per claim as attr.claimLabel); clearing it returns the claim to the computed number.

Fidelity

The theme is not a lookalike: it is the argument-mapping theme JSON extracted from the embedded theme object of a .mup file saved by the MindMup product (app/js/themes.js, engine/theme-argmap.js), plus the fonts MindMup used (NotoSans for claims, Architects Daughter for stickies). Per-map embedded themes, author-set node widths, connector-width overrides, links and attachments in real .mup files are honored by the engine as-is. Known gaps: CSS dashed borders draw slightly shorter dashes than MindMup's renderer, and the argMappingHighImpact theme is reconstructed (base theme + "because…" / "but…" connector labels) rather than extracted.

Repo layout

app/           the editor (static ES modules; app/bundle.js is the engine)
engine/        vendored mapjs source + build script (see engine/README.md)
engine-demo/   raw engine playground (drag a .mup onto it; ?src=&labels=0)
samples/       synthetic .mup fixtures safe for a public repo
samples-local/ real course maps — gitignored, never commit
site/          the landing page and its root-level pages (/privacy, /terms)
figures/       the landing page's argument-map figures: source maps + renderer
test/          nine e2e suites (Chrome + real WebKit) and render-map.js (headless renders)
docs/          rendered proofs

The maps on the landing page are live argument maps in the editor's own grammar, pre-rendered from figures/maps/*.json and committed — including the .mup each figure offers for download and hands to the editor. Edit the JSON, rerun node figures/build.mjs: see docs/figures.md.

Tests: cd test && npm ci, then npm test. The runner serves the repo root and runs all nine suites in order: the Chrome ones via puppeteer-core (app-e2e.js, robustness-e2e.js — blocked storage and unreadable files, click-select-e2e.js, drive-e2e.js, onedrive-e2e.js, features-e2e.js), then webkit-e2e.js (Playwright WebKit, the Safari-engine check), a11y-e2e.js (WCAG 2.2 AA gate: axe-core scans plus the keyboard model, also WebKit — see docs/accessibility.md) and site-e2e.js (the landing page's figures, both engines). npm test -- app-e2e.js runs only the suites named. It needs a system Chrome (or CHROME_PATH pointing at one) and Playwright WebKit (npx playwright-core install webkit). All nine must pass before deploying.

License

MIT — see LICENSE. Copyright (c) 2026 Simon Cullen.

The vendored rendering engine (mindmup/mapjs) and everything compiled into app/bundle.js are MIT too; the two bundled fonts are under the SIL Open Font License 1.1. Their notices are collected in THIRD-PARTY-NOTICES.md, with the font license text next to the fonts in app/fonts/OFL.txt.