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+# Card Layout Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Wrap each old Reddit post in a shadcn-styled card with configurable gap, page background, and independent toggle from badges.
+
+**Architecture:** Add `rt-card` class to each `div.thing.link` via JS, apply card styling via scoped CSS. Convert internal float layout to flexbox. Shared dark mode detection in `settings.js`. Unified MutationObserver in `main.js` for both badge and card processing.
+
+**Tech Stack:** Vanilla JS (IIFE modules on `window.RedditTweaks`), plain CSS, Firefox WebExtension manifest v2.
+
+## Global Constraints
+
+- old.reddit.com only — `www.reddit.com` is out of scope
+- No build tools, no frameworks, no npm dependencies
+- All CSS values for the card must match shadcn/ui's default neutral theme exactly (see spec `docs/superpowers/specs/2026-08-26-card-layout-design.md` for token table)
+- Modules use IIFE pattern and expose API on `window.RedditTweaks`
+- Imports at top of file, no inline imports
+
+---
+
+### Task 1: Extract shared utilities to `settings.js`
+
+Move `isDarkMode()` and `getColorPrefix()` from `badges.js` into `settings.js` as shared infrastructure. Add new setting defaults. Update all consumers.
+
+**Files:**
+- Modify: `lib/settings.js`
+- Modify: `content/tweaks/badges.js`
+- Modify: `content/tweaks/color-popover.js`
+
+**Interfaces:**
+- Produces: `window.RedditTweaks.isDarkMode(settings)` → `boolean`
+- Produces: `window.RedditTweaks.getColorPrefix(settings)` → `"light" | "dark"`
+- Produces: New DEFAULTS keys: `badgeLayout` (true), `cardLayout` (true), `cardBackground` ("reddit"), `cardGap` (16)
+
+- [ ] **Step 1: Add dark mode functions and new defaults to `settings.js`**
+
+Add `isDarkMode`, `getColorPrefix`, and new setting keys to `lib/settings.js`. Insert after the `resetSettings` function, before the `window.RedditTweaks` assignment:
+
+```js
+function isDarkMode(settings) {
+  if (settings.darkMode === "light") return false;
+  if (settings.darkMode === "dark") return true;
+  return document.body.classList.contains("res-nightmode");
+}
+
+function getColorPrefix(settings) {
+  return isDarkMode(settings) ? "dark" : "light";
+}
+```
+
+Add to `DEFAULTS`:
+
+```js
+badgeLayout: true,
+cardLayout: true,
+cardBackground: "reddit",
+cardGap: 16,
+```
+
+Add to the `window.RedditTweaks` assignment:
+
+```js
+window.RedditTweaks.isDarkMode = isDarkMode;
+window.RedditTweaks.getColorPrefix = getColorPrefix;
+```
+
+- [ ] **Step 2: Update `badges.js` to use shared functions**
+
+In `content/tweaks/badges.js`:
+
+Remove the `isDarkMode` and `getColorPrefix` function definitions (lines 8-17).
+
+Replace all internal calls to `isDarkMode(settings)` with `window.RedditTweaks.isDarkMode(settings)` and `getColorPrefix(settings)` with `window.RedditTweaks.getColorPrefix(settings)`.
+
+Update the exported API — keep `isDarkMode` and `getColorPrefix` as aliases for backward compatibility during this transition, but point them at the shared versions:
+
+```js
+window.RedditTweaks.badgeTweak = {
+  apply: apply,
+  updateColors: updateColors,
+  isDarkMode: window.RedditTweaks.isDarkMode,
+  getColorPrefix: window.RedditTweaks.getColorPrefix,
+};
+```
+
+- [ ] **Step 3: Update `color-popover.js` to use shared functions**
+
+In `content/tweaks/color-popover.js`, change the `getHelpers()` function (lines 16-21):
+
+```js
+function getHelpers() {
+  return {
+    isDarkMode: window.RedditTweaks.isDarkMode,
+    getColorPrefix: window.RedditTweaks.getColorPrefix,
+  };
+}
+```
+
+- [ ] **Step 4: Verify extension still works**
+
+Load the extension in Firefox (`about:debugging` → Load Temporary Add-on). Navigate to `old.reddit.com`. Verify:
+- Badges render with correct colors
+- Dark mode detection works (if RES is installed, toggle night mode)
+- Color popover opens and displays correct mode
+- No console errors
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add lib/settings.js content/tweaks/badges.js content/tweaks/color-popover.js
+git commit -m "refactor: extract isDarkMode/getColorPrefix to settings.js as shared utilities"
+```
+
+---
+
+### Task 2: Badge layout toggle + FOUC CSS rename
+
+Add `badgeLayout` toggle to the popup and gate badge processing behind it. Rename the FOUC CSS class from `rt-enabled` to `rt-badges-enabled`.
+
+**Files:**
+- Modify: `content/styles/badges.css`
+- Modify: `content/main.js`
+- Modify: `popup/popup.html`
+- Modify: `popup/popup.js`
+
+**Interfaces:**
+- Consumes: `settings.badgeLayout` (boolean, from Task 1 DEFAULTS)
+- Produces: `html.rt-badges-enabled` class on `<html>` (replaces `html.rt-enabled`)
+
+- [ ] **Step 1: Rename FOUC selectors in `badges.css`**
+
+In `content/styles/badges.css`, change the FOUC prevention selectors (lines 1-5):
+
+From:
+```css
+html.rt-enabled .thing.link .tagline .subreddit,
+html.rt-enabled .thing.link .flat-list li:has(> .comments) {
+  display: none !important;
+}
+```
+
+To:
+```css
+html.rt-badges-enabled .thing.link .tagline .subreddit,
+html.rt-badges-enabled .thing.link .flat-list li:has(> .comments) {
+  display: none !important;
+}
+```
+
+- [ ] **Step 2: Update `main.js` to gate badges behind `badgeLayout`**
+
+Replace the `init()` function in `content/main.js`:
+
+```js
+async function init() {
+  const settings = await window.RedditTweaks.loadSettings();
+  if (!settings.enabled) return;
+
+  if (settings.badgeLayout) {
+    document.documentElement.classList.add("rt-badges-enabled");
+    window.RedditTweaks.badgeTweak.apply(settings);
+  }
+
+  browser.storage.onChanged.addListener(function (changes) {
+    if (
+      (changes.enabled && changes.enabled.newValue !== changes.enabled.oldValue) ||
+      (changes.badgeLayout && changes.badgeLayout.newValue !== changes.badgeLayout.oldValue)
+    ) {
+      location.reload();
+      return;
+    }
+
+    window.RedditTweaks.loadSettings().then(function (updated) {
+      if (settings.badgeLayout) {
+        window.RedditTweaks.badgeTweak.updateColors(updated);
+      }
+    });
+  });
+}
+```
+
+- [ ] **Step 3: Add badge toggle to popup HTML**
+
+In `popup/popup.html`, add a badge toggle after the existing enabled checkbox. Change the first section:
+
+```html
+<div class="section">
+  <label class="toggle-row">
+    <span>Enabled</span>
+    <input type="checkbox" id="enabled">
+  </label>
+  <label class="toggle-row">
+    <span>Badge layout</span>
+    <input type="checkbox" id="badgeLayout">
+  </label>
+</div>
+```
+
+- [ ] **Step 4: Wire badge toggle in `popup.js`**
+
+In `popup/popup.js`, add `badgeLayout` to the `populateControls` function:
+
+```js
+document.getElementById("badgeLayout").checked = settings.badgeLayout;
+```
+
+Add change listener in `init()`, next to the existing `enabled` listener:
+
+```js
+document.getElementById("badgeLayout").addEventListener("change", saveFromControls);
+```
+
+Add to `saveFromControls()` — in the settings object construction, add:
+
+```js
+badgeLayout: document.getElementById("badgeLayout").checked,
+```
+
+- [ ] **Step 5: Verify badge toggle works**
+
+Reload extension. Open popup:
+- Badge layout checkbox is checked by default
+- Unchecking it and reloading old.reddit.com: original subreddit/comment links are visible, no badges
+- Checking it back: badges return after reload
+- No console errors
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add content/styles/badges.css content/main.js popup/popup.html popup/popup.js
+git commit -m "feat: add badgeLayout toggle, rename FOUC class to rt-badges-enabled"
+```
+
+---
+
+### Task 3: Create card CSS
+
+Create `content/styles/cards.css` with all card styling per the spec. Add it to the manifest.
+
+**Files:**
+- Create: `content/styles/cards.css`
+- Modify: `manifest.json`
+
+**Interfaces:**
+- Produces: CSS rules scoped under `.rt-card`, `html.rt-card-enabled`, `html.rt-card-bg-shadcn`
+
+- [ ] **Step 1: Create `content/styles/cards.css`**
+
+```css
+/* --- Post list container --- */
+html.rt-card-enabled #siteTable {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  gap: var(--rt-card-gap, 1rem);
+}
+
+html.rt-card-enabled #siteTable > .clearleft {
+  display: none;
+}
+
+/* --- Card container --- */
+.rt-card {
+  background: #ffffff;
+  color: #0a0a0a;
+  border: 1px solid #e5e5e5;
+  border-radius: 0.875rem;
+  padding: 1.5rem;
+  box-shadow: 0 1px 2px 0 rgb(0 0 0 / 0.05);
+  transition: border-color 0.15s;
+  display: flex;
+  align-items: flex-start;
+  gap: 0.75rem;
+  width: 100%;
+  overflow: hidden;
+}
+
+.rt-card:hover {
+  border-color: #d4d4d4;
+}
+
+/* --- Card internal layout overrides --- */
+.rt-card .midcol,
+.rt-card .thumbnail {
+  float: none;
+  flex-shrink: 0;
+}
+
+.rt-card .entry {
+  flex: 1;
+  min-width: 0;
+}
+
+.rt-card .clearleft {
+  display: none;
+}
+
+/* --- Card dark mode --- */
+.rt-dark .rt-card {
+  background: #171717;
+  color: #fafafa;
+  border-color: rgba(255, 255, 255, 0.1);
+}
+
+.rt-dark .rt-card:hover {
+  border-color: rgba(255, 255, 255, 0.18);
+}
+
+/* --- Page background override --- */
+html.rt-card-bg-shadcn .content[role="main"] {
+  background: #f5f5f5;
+}
+
+html.rt-card-bg-shadcn.rt-dark .content[role="main"] {
+  background: #262626;
+}
+```
+
+- [ ] **Step 2: Add `cards.css` to `manifest.json`**
+
+In the `content_scripts[0].css` array, add `content/styles/cards.css` after `badges.css`:
+
+```json
+"css": ["content/styles/badges.css", "content/styles/cards.css"],
+```
+
+- [ ] **Step 3: Verify no parse errors**
+
+Reload extension. Open `old.reddit.com`. No console CSS parse errors. Cards don't render yet (no JS adding the `rt-card` class), but the CSS is loaded.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add content/styles/cards.css manifest.json
+git commit -m "feat: add card CSS with shadcn design tokens"
+```
+
+---
+
+### Task 4: Create card JS + unified observer
+
+Create the card tweak module. Refactor `main.js` to use a single shared MutationObserver that dispatches to both badge and card processors. Remove the duplicate observer from `badges.js`.
+
+**Files:**
+- Create: `content/tweaks/cards.js`
+- Modify: `content/tweaks/badges.js`
+- Modify: `content/main.js`
+- Modify: `manifest.json`
+
+**Interfaces:**
+- Consumes: `window.RedditTweaks.isDarkMode(settings)` (from Task 1)
+- Consumes: `settings.cardLayout`, `settings.cardBackground`, `settings.cardGap` (from Task 1)
+- Produces: `window.RedditTweaks.cardTweak.apply(settings)` — processes posts + applies card classes
+- Produces: `window.RedditTweaks.cardTweak.updateSettings(settings)` — live-update gap/background
+- Produces: `window.RedditTweaks.cardTweak.processNewPosts(settings)` — process unprocessed posts (called by shared observer)
+- Modifies: `window.RedditTweaks.badgeTweak` — adds `processNewPosts(settings)` for shared observer, removes internal observer
+
+- [ ] **Step 1: Create `content/tweaks/cards.js`**
+
+```js
+(function () {
+  "use strict";
+
+  function processPost(post) {
+    if (post.classList.contains("rt-card")) return;
+    post.classList.add("rt-card");
+  }
+
+  function processPosts() {
+    var posts = document.querySelectorAll("div.thing.link:not(.rt-card)");
+    for (var i = 0; i < posts.length; i++) {
+      processPost(posts[i]);
+    }
+  }
+
+  function applyDarkMode(settings) {
+    if (window.RedditTweaks.isDarkMode(settings)) {
+      document.documentElement.classList.add("rt-dark");
+    } else {
+      document.documentElement.classList.remove("rt-dark");
+    }
+  }
+
+  function applyBackground(settings) {
+    if (settings.cardBackground === "shadcn") {
+      document.documentElement.classList.add("rt-card-bg-shadcn");
+    } else {
+      document.documentElement.classList.remove("rt-card-bg-shadcn");
+    }
+  }
+
+  function applyGap(settings) {
+    var siteTable = document.getElementById("siteTable");
+    if (siteTable) {
+      siteTable.style.setProperty("--rt-card-gap", settings.cardGap + "px");
+    }
+  }
+
+  function apply(settings) {
+    document.documentElement.classList.add("rt-card-enabled");
+    applyDarkMode(settings);
+    applyBackground(settings);
+    applyGap(settings);
+    processPosts();
+  }
+
+  function updateSettings(settings) {
+    applyDarkMode(settings);
+    applyBackground(settings);
+    applyGap(settings);
+  }
+
+  window.RedditTweaks = window.RedditTweaks || {};
+  window.RedditTweaks.cardTweak = {
+    apply: apply,
+    updateSettings: updateSettings,
+    processNewPosts: processPosts,
+  };
+})();
+```
+
+- [ ] **Step 2: Expose `processNewPosts` from `badges.js`, remove both internal observers**
+
+In `content/tweaks/badges.js`:
+
+Remove the `contentObserver` variable declaration (line 4: `let contentObserver = null;`).
+
+Remove the `darkModeObserver` variable declaration (line 5: `let darkModeObserver = null;`).
+
+Remove the `getObserverTarget()` function (lines 106-112).
+
+Remove the `startContentObserver(settings)` function (lines 114-135).
+
+Remove the `startDarkModeObserver()` function (lines 137-149).
+
+Remove both observer calls from the `apply()` function: `startContentObserver(settings)` (line 168) and `startDarkModeObserver()` (line 169).
+
+Add `processNewPosts` to the exported API:
+
+```js
+window.RedditTweaks.badgeTweak = {
+  apply: apply,
+  updateColors: updateColors,
+  isDarkMode: window.RedditTweaks.isDarkMode,
+  getColorPrefix: window.RedditTweaks.getColorPrefix,
+  processNewPosts: processPosts,
+};
+```
+
+- [ ] **Step 3: Add unified observer to `main.js`**
+
+In `content/main.js`, add shared observer functions before `init()`.
+
+First, the dark mode observer (moved from `badges.js`). This watches for RES night mode toggles and dispatches to both modules:
+
+```js
+function startDarkModeObserver(settings) {
+  var observer = new MutationObserver(function () {
+    if (settings.darkMode === "auto") {
+      window.RedditTweaks.loadSettings().then(function (updated) {
+        if (settings.badgeLayout) {
+          window.RedditTweaks.badgeTweak.updateColors(updated);
+        }
+        if (settings.cardLayout) {
+          window.RedditTweaks.cardTweak.updateSettings(updated);
+        }
+      });
+    }
+  });
+
+  observer.observe(document.body, {
+    attributes: true,
+    attributeFilter: ["class"],
+  });
+}
+```
+
+Then the content observer for new posts:
+
+```js
+function startPostObserver(settings) {
+  var target =
+    document.getElementById("siteTable") ||
+    document.querySelector('.content[role="main"]') ||
+    document.body;
+
+  var observer = new MutationObserver(function (mutations) {
+    var hasNewPosts = false;
+    for (var i = 0; i < mutations.length; i++) {
+      var added = mutations[i].addedNodes;
+      for (var j = 0; j < added.length; j++) {
+        var node = added[j];
+        if (node.nodeType !== Node.ELEMENT_NODE) continue;
+        if ((node.matches && node.matches("div.thing.link")) ||
+            (node.querySelector && node.querySelector("div.thing.link"))) {
+          hasNewPosts = true;
+          break;
+        }
+      }
+      if (hasNewPosts) break;
+    }
+    if (hasNewPosts) {
+      window.RedditTweaks.loadSettings().then(function (updated) {
+        if (settings.badgeLayout) {
+          window.RedditTweaks.badgeTweak.processNewPosts(updated);
+        }
+        if (settings.cardLayout) {
+          window.RedditTweaks.cardTweak.processNewPosts(updated);
+        }
+      });
+    }
+  });
+
+  observer.observe(target, { childList: true, subtree: true });
+}
+```
+
+Update `init()` to call `cardTweak.apply`, start the shared observer, and observe dark mode changes for cards:
+
+```js
+async function init() {
+  const settings = await window.RedditTweaks.loadSettings();
+  if (!settings.enabled) return;
+
+  if (settings.badgeLayout) {
+    document.documentElement.classList.add("rt-badges-enabled");
+    window.RedditTweaks.badgeTweak.apply(settings);
+  }
+
+  if (settings.cardLayout) {
+    window.RedditTweaks.cardTweak.apply(settings);
+  }
+
+  if (settings.badgeLayout || settings.cardLayout) {
+    startPostObserver(settings);
+    startDarkModeObserver(settings);
+  }
+
+  browser.storage.onChanged.addListener(function (changes) {
+    if (
+      (changes.enabled && changes.enabled.newValue !== changes.enabled.oldValue) ||
+      (changes.badgeLayout && changes.badgeLayout.newValue !== changes.badgeLayout.oldValue) ||
+      (changes.cardLayout && changes.cardLayout.newValue !== changes.cardLayout.oldValue)
+    ) {
+      location.reload();
+      return;
+    }
+
+    window.RedditTweaks.loadSettings().then(function (updated) {
+      if (settings.badgeLayout) {
+        window.RedditTweaks.badgeTweak.updateColors(updated);
+      }
+      if (settings.cardLayout) {
+        window.RedditTweaks.cardTweak.updateSettings(updated);
+      }
+    });
+  });
+}
+```
+
+- [ ] **Step 4: Add `cards.js` to `manifest.json`**
+
+In the `content_scripts[0].js` array, add `content/tweaks/cards.js` before `main.js`:
+
+```json
+"js": [
+  "lib/settings.js",
+  "content/tweaks/badges.js",
+  "content/tweaks/color-picker.js",
+  "content/tweaks/color-popover.js",
+  "content/tweaks/cards.js",
+  "content/main.js"
+],
+```
+
+Also remove `"*://www.reddit.com/*"` from the `matches` array (out of scope per spec):
+
+```json
+"matches": ["*://old.reddit.com/*"],
+```
+
+- [ ] **Step 5: Verify cards render**
+
+Reload extension. Navigate to `old.reddit.com`:
+- Each post is wrapped in a card: white background, 1px `#e5e5e5` border, 14px rounded corners, subtle shadow
+- Posts are separated by 16px gaps
+- Vote arrows, thumbnail, and entry are horizontally aligned (no floats)
+- Hovering a card darkens the border to `#d4d4d4`
+- Badges still render inside cards (if badge layout is enabled)
+- No console errors
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add content/tweaks/cards.js content/tweaks/badges.js content/main.js manifest.json
+git commit -m "feat: add card layout tweak with unified post observer"
+```
+
+---
+
+### Task 5: Popup controls for card settings
+
+Add card layout controls to the extension popup: enable toggle, background style dropdown, card spacing dropdown.
+
+**Files:**
+- Modify: `popup/popup.html`
+- Modify: `popup/popup.js`
+
+**Interfaces:**
+- Consumes: `settings.cardLayout`, `settings.cardBackground`, `settings.cardGap` (from Task 1 DEFAULTS)
+
+- [ ] **Step 1: Add card layout section to popup HTML**
+
+In `popup/popup.html`, add this section after the Dark Mode section and before the Light Mode Colors section:
+
+```html
+<div class="section">
+  <h2>Card Layout</h2>
+  <label class="toggle-row">
+    <span>Enable card layout</span>
+    <input type="checkbox" id="cardLayout">
+  </label>
+  <label for="cardBackground">Background Style</label>
+  <select id="cardBackground">
+    <option value="reddit">Reddit Default</option>
+    <option value="shadcn">shadcn Style</option>
+  </select>
+  <label for="cardGap">Card Spacing</label>
+  <select id="cardGap">
+    <option value="8">8px</option>
+    <option value="12">12px</option>
+    <option value="16">16px</option>
+    <option value="24">24px</option>
+    <option value="32">32px</option>
+  </select>
+</div>
+```
+
+- [ ] **Step 2: Wire card controls in `popup.js`**
+
+In `populateControls(settings)`, add:
+
+```js
+document.getElementById("cardLayout").checked = settings.cardLayout;
+document.getElementById("cardBackground").value = settings.cardBackground;
+document.getElementById("cardGap").value = String(settings.cardGap);
+```
+
+In `saveFromControls()`, add to the settings object:
+
+```js
+cardLayout: document.getElementById("cardLayout").checked,
+cardBackground: document.getElementById("cardBackground").value,
+cardGap: parseInt(document.getElementById("cardGap").value, 10),
+```
+
+In `init()`, add change listeners:
+
+```js
+document.getElementById("cardLayout").addEventListener("change", saveFromControls);
+document.getElementById("cardBackground").addEventListener("change", saveFromControls);
+document.getElementById("cardGap").addEventListener("change", saveFromControls);
+```
+
+- [ ] **Step 3: Verify settings work end-to-end**
+
+Reload extension. Open popup:
+- Card layout checkbox is checked by default
+- Background dropdown shows "Reddit Default"
+- Card spacing shows "16px"
+- Changing card spacing to "24px": cards on old.reddit.com update gap live (no reload)
+- Changing background to "shadcn Style": page background becomes `#f5f5f5` (live)
+- Unchecking card layout: page reloads, cards disappear, posts show flat list
+- Settings persist after closing and reopening popup
+- Settings persist after browser restart
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add popup/popup.html popup/popup.js
+git commit -m "feat: add card layout controls to extension popup"
+```