Recall — Spaced Repetition Calendar

Anki's algorithm. A calendar you actually want to open.

Anki is effective but its interface is stuck in 2004. Recall gives you the same scientifically-proven SM-2 spaced repetition wrapped in a month-view calendar that makes your entire study schedule visible at a glance. Self-hosted, no sync fees, no card decks — log what you studied and show up when it tells you to.

If Recall is useful to you, consider giving it a ⭐ — it helps others find it.

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Features

Feature	Description
SM-2 Spaced Repetition	Reviews are scheduled at scientifically-optimal intervals (default: +1, +3, +7, +14, +30 days). Confidence ratings adapt future intervals via ease-factor.
Calendar View	Month-view calendar with colour-coded chips: studied sessions, review 1–5, overdue indicators.
Confidence Ratings	Mark reviews with Blank / Hard / Okay / Good / Perfect — the SM-2 algorithm reschedules the next review accordingly.
Forgetting Curve	Per-session exponential decay chart with a full review history table (Done / Upcoming / Overdue) below the chart.
Recurring Sessions	Schedule a topic to auto-recur weekly or at a fixed interval — catch-up instances are created automatically on login.
Drag-and-Drop Reschedule	Drag undone review chips to any other calendar day to reschedule them.
Subject Filter	Filter the calendar by subject (Biology, Languages, Maths…) with one click.
Custom Subject Colors	Pick any color for each subject from Settings → Subject Colors. Overrides the default auto-assigned palette; Reset link shown when a custom color exists.
Tags	Add free-form tags to sessions; filter the calendar by tag from the tag bar.
Full-Text Search	Instant search across topic, notes, subject and tags with match count.
Exam Countdown	Track upcoming exams (name, date, optional subject) in the sidebar. Counts down in days; highlights Tomorrow in amber and Today in red. Past exams collapse under a disclosure row.
Second Brain Links	Connect sessions with typed relations — Builds on, Prerequisite of, Related to, See also — displayed inline in the day modal.
Knowledge Graph	Obsidian-style force-directed graph of all linked sessions with pan, zoom, draggable nodes, and per-subject dimming.
Stats & Heatmap	Activity heatmap (last 13 weeks), per-subject retention bars with overdue count, and per-topic retention list.
Dark Mode	Toggle dark mode — the calendar, modals, and knowledge graph all adapt.
14 Themes	Built-in theme picker with 14 themes (Professional, Pixel Game, Wabi-Sabi, Brutalist, Synthwave, and more). Fully extensible via CSS custom properties.
Custom Intervals	Set your own review intervals (e.g. 1 / 7 / 21 / 60 / 120 days). Changes apply to new sessions going forward.
JWT Auth	Full registration and login; all data is isolated per user.
Flashcard Decks	Create cards manually, import from Anki (.apkg) or .txt, or export back to Anki. Card faces support **bold** and `inline code` markdown. Image cards: paste from clipboard or pick a file — stored as base64 in the card JSON, no server upload needed.
Active Recall Practice	Full-screen study modal: flip with click or Space, rate 1–5 (keyboard shortcuts), 🔊 text-to-speech on every card face, per-card difficulty dot, and a wrong-answer re-queue button to repeat cards rated 1–2 immediately after the session.
Card Difficulty Sort	"↓ Hardest first" button in the deck editor sorts cards by historical average score — unrated and struggling cards surface to the top.
PWA	Installable as a native-feeling app on iOS and Android — works offline, home screen icon, no app store required.

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Screenshots

Populated calendar — studied chips in subject colour, review chips in red → blue gradient.	Confidence rating — rate recall after each review; SM-2 reschedules the next date.
Forgetting curve — per-session exponential decay chart with past and upcoming review markers.	Knowledge graph — Obsidian-style force-directed graph of all linked sessions.
Dark mode — full dark palette across the calendar, modals, and graph.	Stats & heatmap — 13-week activity heatmap and per-subject retention bars.

More screenshots

Add Study Session

Log a new topic with subject, notes, tags, and an optional weekly or interval-based recurrence rule.

Full-text search

Live search filters the calendar to matching sessions. Matches topics, notes, subject, and tags simultaneously.

Subject filter

One-click subject pill hides all other subjects. Physics selected here — only Newton's Laws and Projectile Motion shown.

Day modal — session details, tags & links

Click any day to see all sessions and reviews. Shows tags, second-brain links, forgetting-curve button, and edit/delete controls.

Second brain — link sessions

Link any two sessions with a typed relationship. Choose the relation type and target session — click Save Link to persist.

Knowledge graph — subject focus

Click a subject pill in the graph toolbar to dim non-matching nodes — isolates a discipline's knowledge cluster at a glance.

Drag-and-drop reschedule

Drag any undone review chip to a new calendar day to reschedule it. The server persists the new date immediately.

Settings — custom intervals

Override the default SM-2 intervals with any values you prefer. Preview dates update live as you type.

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Getting Started

Prerequisites

• Node.js 18 or later
• npm

Install & run (Docker)

The easiest way to run Recall is using Docker Compose. This automatically provisions the environment and sets up a persistent volume for your database.

git clone https://github.com/Garuda8887/recall.git
cd recall
docker compose up -d

Open http://localhost:3000 in your browser. Your database is automatically saved to a local ./data folder so it persists across container restarts.

To apply future updates, simply pull the latest code and rebuild:

git pull
docker compose up -d --build

Install & run (Manual)

git clone https://github.com/Garuda8887/recall.git
cd recall
npm install
node server.js

Open http://localhost:3000 in your browser, register an account, and start logging sessions.

Environment variables

Variable	Default	Description
PORT	3000	HTTP port
JWT_SECRET	recall-dev-secret-please-change-in-production	Change this in production

JWT_SECRET=my-super-secret-key PORT=8080 node server.js

Install as an app (PWA)

Recall is a fully installable Progressive Web App — no app store required.

Platform	How to install
iOS / iPadOS	Open in Safari → Share → Add to Home Screen
Android	Open in Chrome → three-dot menu → Add to Home Screen (or accept the install prompt)
Desktop (Chrome / Edge)	Click the install icon in the address bar

Once installed it launches fullscreen with its own icon, just like a native app. It also works offline — the app shell is cached locally so the UI loads instantly even without a connection (data syncs when you're back online).

Updating: just git pull on your server. The service worker detects the new version and refreshes automatically on next open — no reinstall needed.

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How it works

SM-2 algorithm

After each review you rate your recall from 1 (blank) to 5 (perfect). SM-2 uses that score to grow or shrink the next interval — ace it repeatedly and reviews get pushed further out; struggle and it resets to the next day. The default schedule after a new session is +1 · +3 · +7 · +14 · +30 days, fully customisable in Settings.

Flashcard decks

After logging a session you're prompted to attach a flashcard deck — create cards manually or import from an existing file. Three import paths are supported:

Format	How
Anki .apkg	Choose the file in the import dialog; the server extracts the SQLite database from the ZIP and parses all notes automatically. HTML formatting is stripped.
Text .txt	Tab-separated, pipe-separated, or comma-separated front / back pairs — one card per line. Lines starting with # are treated as comments.
Manual	Type cards directly in the deck editor; Tab from the last field adds a new row.

Decks can be exported back to a tab-separated .txt compatible with Anki's plain-text import.

Card content — each card face can be:

• Text with markdown — **bold**, `inline code`, and newlines are rendered during study. The deck editor stays plain text for easy editing.
• An image — paste an image from your clipboard directly into a card field, or click 📷 to pick a file. The image is stored as a base64 data URL inside the card JSON — no server upload, no external URLs.

The deck editor also has a "↓ Hardest first" button that sorts your cards by historical average score, putting the ones you've been getting wrong at the top so you can focus on weak spots.

Once a deck is attached, a Practice button appears next to "Mark done" wherever that review surfaces — in the due-today banner on the main calendar and inside the day modal. Clicking Practice opens the study modal so you never lose your place. After going through the last card a score screen shows your results; if any cards were rated 1–2, an ↻ Re-study N weak cards button lets you repeat just those cards immediately. You can also study again in full or close and mark the review done.

Each card face has a 🔊 text-to-speech button (browser-native speechSynthesis, no API key needed) — useful for language learning or studying with eyes closed.

Recurring sessions

Set a session to recur every Tuesday or every N days. Any missed instances since the last login are auto-created (capped at 14 catch-ups per series).

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Tech stack

Layer	Technology
Server	Node.js + Express
Database	SQLite via better-sqlite3 (zero-config, single file)
Auth	JWT (jsonwebtoken) + bcrypt
Frontend	Vanilla HTML/CSS/JS — single-file SPA (public/index.html)
Graph	Custom force-directed simulation (Coulomb repulsion + Hooke springs + gravity) rendered in SVG

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Theming

Recall ships with 14 built-in themes — including Professional, Pixel Game, Wabi-Sabi, Brutalist, Dark Synthwave, and more — switchable from the sidebar (☰ → Settings → Theme). Themes persist across reloads via localStorage.

How the system works

• Themes are driven by a data-theme attribute on <body> (e.g. data-theme="pixel").
• Each theme is a self-contained CSS block in public/style.css scoped to [data-theme="yourtheme"] — the default styles are never touched.
• The JS THEMES array in public/index.html registers each theme for the picker UI.

Adding a new theme

1. Register it in the picker — find the THEMES array near the top of the <script> block in public/index.html and add an entry:

{
  id: 'mytheme',           // matches data-theme value
  name: 'My Theme',        // shown in the picker
  desc: 'One-line mood',   // shown below the name
  swatches: ['#bg','#accent','#secondary','#text'], // four preview dots
},

2. Write the CSS block — append to the bottom of public/style.css:

/* ── My Theme ── */
[data-theme="mytheme"] {
  /* Design tokens — override as many or as few as you need */
  --ff:          'Your Font', sans-serif;
  --ff-heading:  'Your Font', sans-serif;
  --bg:          #…;   /* page background */
  --surface:     #…;   /* card / modal background */
  --surface-2:   #…;   /* secondary surfaces */
  --border:      #…;   /* primary border colour */
  --border-soft: #…;   /* subtle borders */
  --tx:          #…;   /* primary text */
  --tx-2:        #…;   /* secondary text */
  --tx-3:        #…;   /* muted / placeholder text */
  --accent:      #…;   /* buttons, highlights, today badge */
  --accent-dk:   #…;   /* darker accent for hover states */
  --accent-bg:   #…;   /* light accent tint (badges, chips) */
  --accent-glow: rgba(…, 0.18); /* active-card glow in the picker */
  --sh-xs: …;  --sh-sm: …;  --sh-md: …;  --sh-lg: …; /* shadows */
  --r-xs: …;   --r-sm: …;   --r-md: …;   --r-lg: …;  --r-xl: …; /* radii */
}

/* Structural overrides — only what the token system can't handle */
[data-theme="mytheme"] header { … }
[data-theme="mytheme"] .logo  { … }
/* … etc */

/* Optional dark variant */
[data-theme="mytheme"].dark { … }

3. Add the font (if needed) — extend the single @import at the top of style.css:

@import url('https://fonts.googleapis.com/css2?…&family=YourFont&display=swap');

That's it — the picker renders automatically, selection is saved to localStorage, and the data-theme attribute is applied on page load before first paint.

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API reference

All session routes require Authorization: Bearer <token>.

Method	Path	Description
POST	/api/auth/register	Register { email, password }
POST	/api/auth/login	Login → returns JWT
GET	/api/auth/me	Verify token
GET	/api/sessions	List all sessions (auto-creates due recurrences)
POST	/api/sessions	Create a session
PUT	/api/sessions/:id	Update topic / subject / notes / tags
DELETE	/api/sessions/:id	Delete session and its links
PATCH	/api/sessions/:id/reviews/:index	Mark done (with confidence + SM-2), undo, or reschedule (newDate)
GET	/api/links	List knowledge-graph links
POST	/api/links	Create a link { fromId, toId, relation }
DELETE	/api/links/:id	Remove a link
GET	/api/settings	Get custom intervals
PUT	/api/settings	Save custom intervals
GET	/api/decks	List all decks for the user
POST	/api/decks	Create a deck { session_id, name, cards }
PUT	/api/decks/:id	Update deck name or cards
DELETE	/api/decks/:id	Delete a deck
POST	/api/decks/parse-apkg	Parse an Anki .apkg file (binary body) → returns { cards }

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License

MIT © Garuda8887

Free to use, copy, modify and distribute. The copyright notice above must be included in all copies or substantial portions of the software — if you build on this, you must credit the original author.

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Built with ❤️ as a self-hosted alternative to Anki, optimised for visual learners who think in calendars.