diff --git a/web/src/app.css b/web/src/app.css
index 603ca35..b916c55 100644
--- a/web/src/app.css
+++ b/web/src/app.css
@@ -41,6 +41,15 @@
   --nav-width: 232px;
   --shadow-cover: 0 1px 2px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.35);
   --shadow-lift: 0 12px 32px rgba(0, 0, 0, 0.5);
+
+  /* User-controlled sizing. --ui-scale drives every rem in the app, so the
+     text-size setting scales headings, labels and body together. --card-scale
+     drives cover widths in shelves and grids, so card size is independent of
+     text size. Both are set from the Appearance panel and persisted locally. */
+  --ui-scale: 1;
+  --card-scale: 1;
+  --card-w: calc(160px * var(--card-scale));
+  --grid-min: calc(158px * var(--card-scale));
 }
 
 @media (prefers-color-scheme: light) {
@@ -73,11 +82,18 @@ body,
   margin: 0;
 }
 
+html {
+  /* The single root size every rem is relative to. 15px is a deliberate ~7%
+     increase over the previous 14px baseline; the Appearance panel multiplies
+     it via --ui-scale. */
+  font-size: calc(15px * var(--ui-scale));
+}
+
 body {
   background: var(--bg);
   color: var(--text);
   font-family: var(--font);
-  font-size: 14px;
+  font-size: 1rem;
   line-height: 1.5;
   -webkit-font-smoothing: antialiased;
 }
@@ -98,13 +114,13 @@ h3 {
   letter-spacing: -0.015em;
 }
 h1 {
-  font-size: 22px;
+  font-size: 1.571rem;
 }
 h2 {
-  font-size: 17px;
+  font-size: 1.214rem;
 }
 h3 {
-  font-size: 15px;
+  font-size: 1.071rem;
 }
 
 button,
@@ -158,7 +174,7 @@ select {
 }
 .btn-lg {
   padding: 11px 22px;
-  font-size: 15px;
+  font-size: 1.071rem;
   border-radius: 12px;
 }
 
@@ -183,7 +199,7 @@ select {
   gap: 6px;
 }
 .field label {
-  font-size: 12px;
+  font-size: .857rem;
   font-weight: 500;
   color: var(--muted);
 }
@@ -201,7 +217,7 @@ select {
   padding: 2px 8px;
   border-radius: 999px;
   border: 1px solid var(--border-strong);
-  font-size: 11px;
+  font-size: .786rem;
   color: var(--muted);
   text-transform: uppercase;
   letter-spacing: 0.05em;
@@ -214,7 +230,7 @@ select {
   background: transparent;
   color: var(--muted);
   cursor: pointer;
-  font-size: 13px;
+  font-size: .929rem;
 }
 .chip:hover {
   color: var(--text);
@@ -231,14 +247,14 @@ select {
   border: 1px solid color-mix(in srgb, var(--danger) 45%, var(--border));
   border-radius: var(--radius);
   background: color-mix(in srgb, var(--danger) 10%, transparent);
-  font-size: 13px;
+  font-size: .929rem;
 }
 .ok {
   padding: 10px 14px;
   border: 1px solid color-mix(in srgb, var(--success) 40%, var(--border));
   border-radius: var(--radius);
   background: color-mix(in srgb, var(--success) 9%, transparent);
-  font-size: 13px;
+  font-size: .929rem;
 }
 
 .muted {
@@ -249,7 +265,7 @@ select {
 }
 .mono {
   font-family: var(--mono);
-  font-size: 12px;
+  font-size: .857rem;
 }
 
 /* ── Cover card ─────────────────────────────────────────────────────── */
@@ -277,7 +293,7 @@ select {
   inset: 0;
   display: grid;
   place-items: center;
-  font-size: 34px;
+  font-size: 2.429rem;
   font-weight: 700;
   color: var(--faint);
   background: linear-gradient(150deg, var(--surface-2), var(--surface-3));
diff --git a/web/src/lib/components/AudiobookPlayer.svelte b/web/src/lib/components/AudiobookPlayer.svelte
index 752f1e9..45a5ef2 100644
--- a/web/src/lib/components/AudiobookPlayer.svelte
+++ b/web/src/lib/components/AudiobookPlayer.svelte
@@ -238,7 +238,7 @@
   .times {
     display: flex;
     justify-content: space-between;
-    font-size: 12px;
+    font-size: .857rem;
   }
   .controls {
     display: flex;
diff --git a/web/src/lib/components/Browse.svelte b/web/src/lib/components/Browse.svelte
index 4f58b0c..7668f60 100644
--- a/web/src/lib/components/Browse.svelte
+++ b/web/src/lib/components/Browse.svelte
@@ -72,7 +72,7 @@
   }
   .grid {
     display: grid;
-    grid-template-columns: repeat(auto-fill, minmax(148px, 1fr));
+    grid-template-columns: repeat(auto-fill, minmax(var(--grid-min), 1fr));
     gap: var(--space-5) var(--space-4);
   }
   .skeleton.tile {
@@ -80,7 +80,7 @@
   }
   @media (max-width: 700px) {
     .grid {
-      grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
+      grid-template-columns: repeat(auto-fill, minmax(calc(var(--grid-min) * 0.75), 1fr));
       gap: var(--space-4) var(--space-3);
     }
   }
diff --git a/web/src/lib/components/Card.svelte b/web/src/lib/components/Card.svelte
index 4cd19f7..801a445 100644
--- a/web/src/lib/components/Card.svelte
+++ b/web/src/lib/components/Card.svelte
@@ -77,7 +77,7 @@
     min-width: 0;
   }
   .title {
-    font-size: 13px;
+    font-size: .929rem;
     font-weight: 500;
     color: var(--text);
     overflow: hidden;
@@ -88,7 +88,7 @@
     line-height: 1.3;
   }
   .subtitle {
-    font-size: 11.5px;
+    font-size: .821rem;
     color: var(--faint);
     overflow: hidden;
     text-overflow: ellipsis;
@@ -102,7 +102,7 @@
     border-radius: 999px;
     background: rgba(0, 0, 0, 0.66);
     color: #fff;
-    font-size: 11px;
+    font-size: .786rem;
     font-weight: 600;
     backdrop-filter: blur(4px);
   }
@@ -122,9 +122,9 @@
     background: var(--accent);
   }
   .sm .title {
-    font-size: 12px;
+    font-size: .857rem;
   }
   .lg .title {
-    font-size: 14px;
+    font-size: 1.000rem;
   }
 </style>
diff --git a/web/src/lib/components/GamePlayer.svelte b/web/src/lib/components/GamePlayer.svelte
index 01d0b31..f942cc8 100644
--- a/web/src/lib/components/GamePlayer.svelte
+++ b/web/src/lib/components/GamePlayer.svelte
@@ -173,7 +173,7 @@
   }
   .status {
     margin: 0 0 var(--space-3);
-    font-size: 13px;
+    font-size: .929rem;
   }
   .stage {
     height: calc(100vh - 60px - 150px);
diff --git a/web/src/lib/components/Home.svelte b/web/src/lib/components/Home.svelte
index c68b23c..2134e21 100644
--- a/web/src/lib/components/Home.svelte
+++ b/web/src/lib/components/Home.svelte
@@ -107,7 +107,7 @@
 <style>
   .hello {
     margin: 0 0 var(--space-5);
-    font-size: 15px;
+    font-size: 1.071rem;
   }
   .explore {
     margin-top: var(--space-2);
@@ -121,14 +121,14 @@
     margin-bottom: var(--space-4);
   }
   .explore h2 {
-    font-size: 17px;
+    font-size: 1.214rem;
   }
   .small {
-    font-size: 12.5px;
+    font-size: .893rem;
   }
   .grid {
     display: grid;
-    grid-template-columns: repeat(auto-fill, minmax(148px, 1fr));
+    grid-template-columns: repeat(auto-fill, minmax(var(--grid-min), 1fr));
     gap: var(--space-5) var(--space-4);
   }
   .loading {
@@ -144,7 +144,7 @@
   .skeleton-row {
     display: grid;
     grid-auto-flow: column;
-    grid-auto-columns: 150px;
+    grid-auto-columns: var(--card-w);
     gap: var(--space-4);
     overflow: hidden;
   }
@@ -153,7 +153,7 @@
   }
   @media (max-width: 700px) {
     .grid {
-      grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
+      grid-template-columns: repeat(auto-fill, minmax(calc(var(--grid-min) * 0.75), 1fr));
       gap: var(--space-4) var(--space-3);
     }
   }
diff --git a/web/src/lib/components/ItemDetail.svelte b/web/src/lib/components/ItemDetail.svelte
index 066c0b7..d876357 100644
--- a/web/src/lib/components/ItemDetail.svelte
+++ b/web/src/lib/components/ItemDetail.svelte
@@ -141,18 +141,18 @@
     padding-top: var(--space-2);
   }
   .kind {
-    font-size: 12px;
+    font-size: .857rem;
     text-transform: uppercase;
     letter-spacing: 0.06em;
     color: var(--accent);
   }
   h1 {
-    font-size: 30px;
+    font-size: 2.143rem;
     line-height: 1.15;
   }
   .byline {
     margin: 0;
-    font-size: 15px;
+    font-size: 1.071rem;
     color: var(--muted);
   }
   .resume {
@@ -173,7 +173,7 @@
     background: var(--accent);
   }
   .resume .muted {
-    font-size: 12px;
+    font-size: .857rem;
   }
   .actions {
     display: flex;
@@ -196,7 +196,7 @@
     margin-bottom: var(--space-2);
     color: var(--muted);
     font-weight: 500;
-    font-size: 13px;
+    font-size: .929rem;
   }
   .tracks ol {
     list-style: none;
@@ -209,7 +209,7 @@
     gap: var(--space-3);
     padding: 6px 0;
     border-bottom: 1px solid var(--border);
-    font-size: 13px;
+    font-size: .929rem;
   }
   .tracks li:last-child {
     border-bottom: none;
diff --git a/web/src/lib/components/Libraries.svelte b/web/src/lib/components/Libraries.svelte
index 7f8071f..79ee7d5 100644
--- a/web/src/lib/components/Libraries.svelte
+++ b/web/src/lib/components/Libraries.svelte
@@ -191,7 +191,7 @@
     background: var(--bg-hover);
   }
   .kind {
-    font-size: 11px;
+    font-size: .786rem;
     text-transform: uppercase;
     letter-spacing: 0.05em;
     color: var(--accent);
@@ -215,7 +215,7 @@
     border-radius: var(--radius);
     background: color-mix(in srgb, var(--success) 8%, transparent);
     margin-bottom: var(--space-4);
-    font-size: 13px;
+    font-size: .929rem;
   }
   .alert {
     margin-bottom: var(--space-4);
diff --git a/web/src/lib/components/Login.svelte b/web/src/lib/components/Login.svelte
index b7a1485..163e532 100644
--- a/web/src/lib/components/Login.svelte
+++ b/web/src/lib/components/Login.svelte
@@ -98,7 +98,7 @@
   }
   .lead {
     margin: -8px 0 0;
-    font-size: 13px;
+    font-size: .929rem;
   }
   .submit {
     justify-content: center;
diff --git a/web/src/lib/components/Reader.svelte b/web/src/lib/components/Reader.svelte
index 03db064..3555995 100644
--- a/web/src/lib/components/Reader.svelte
+++ b/web/src/lib/components/Reader.svelte
@@ -172,13 +172,13 @@
     flex: 1;
   }
   .info strong {
-    font-size: 13px;
+    font-size: .929rem;
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
   }
   .info .muted {
-    font-size: 12px;
+    font-size: .857rem;
   }
   .pct {
     color: var(--text-faint);
diff --git a/web/src/lib/components/SearchResults.svelte b/web/src/lib/components/SearchResults.svelte
index 77e5f2c..f3308d3 100644
--- a/web/src/lib/components/SearchResults.svelte
+++ b/web/src/lib/components/SearchResults.svelte
@@ -68,7 +68,7 @@
 <style>
   .count {
     margin: 0 0 var(--space-5);
-    font-size: 13px;
+    font-size: .929rem;
   }
   section {
     margin-bottom: var(--space-6);
@@ -78,7 +78,7 @@
   }
   .grid {
     display: grid;
-    grid-template-columns: repeat(auto-fill, minmax(148px, 1fr));
+    grid-template-columns: repeat(auto-fill, minmax(var(--grid-min), 1fr));
     gap: var(--space-5) var(--space-4);
   }
   .skeleton.tile {
diff --git a/web/src/lib/components/Settings.svelte b/web/src/lib/components/Settings.svelte
new file mode 100644
index 0000000..542e61a
--- /dev/null
+++ b/web/src/lib/components/Settings.svelte
@@ -0,0 +1,178 @@
+<script lang="ts">
+  import { settings, setSettings, resetSettings, TEXT_STEPS, CARD_STEPS } from '../settings'
+
+  function isActive(current: number, value: number): boolean {
+    return Math.abs(current - value) < 0.001
+  }
+</script>
+
+<div class="wrap">
+  <p class="muted intro">
+    These preferences are saved on this device only, so a TV and a laptop can
+    each have their own.
+  </p>
+
+  <section class="card group">
+    <header>
+      <h3>Text size</h3>
+      <span class="muted small">{Math.round($settings.textScale * 100)}%</span>
+    </header>
+    <div class="segmented">
+      {#each TEXT_STEPS as step (step.label)}
+        <button
+          class="seg"
+          class:active={isActive($settings.textScale, step.value)}
+          onclick={() => setSettings({ textScale: step.value })}
+        >
+          {step.label}
+        </button>
+      {/each}
+    </div>
+  </section>
+
+  <section class="card group">
+    <header>
+      <h3>Card size</h3>
+      <span class="muted small">{Math.round($settings.cardScale * 100)}%</span>
+    </header>
+    <div class="segmented">
+      {#each CARD_STEPS as step (step.label)}
+        <button
+          class="seg"
+          class:active={isActive($settings.cardScale, step.value)}
+          onclick={() => setSettings({ cardScale: step.value })}
+        >
+          {step.label}
+        </button>
+      {/each}
+    </div>
+  </section>
+
+  <section class="group">
+    <h3 class="preview-heading">Preview</h3>
+    <div class="preview">
+      <div class="mock">
+        <div class="mock-cover">A</div>
+        <span class="mock-title">A Long Book Title</span>
+        <span class="mock-sub">3 views</span>
+      </div>
+      <div class="mock">
+        <div class="mock-cover alt">B</div>
+        <span class="mock-title">Another Title</span>
+        <span class="mock-sub">More by an author</span>
+      </div>
+      <div class="mock">
+        <div class="mock-cover alt2">C</div>
+        <span class="mock-title">Third Item</span>
+        <span class="mock-sub">42%</span>
+      </div>
+    </div>
+    <p class="sample muted">
+      Body text looks like this. Headings, labels, and captions all scale
+      together, while card size is controlled separately.
+    </p>
+  </section>
+
+  <button class="btn" onclick={resetSettings}>Reset to defaults</button>
+</div>
+
+<style>
+  .wrap {
+    max-width: 720px;
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-5);
+  }
+  .intro {
+    margin: 0;
+    font-size: 0.929rem;
+  }
+  .group {
+    padding: var(--space-4);
+  }
+  .group header {
+    display: flex;
+    align-items: baseline;
+    justify-content: space-between;
+    margin-bottom: var(--space-3);
+  }
+  h3 {
+    font-size: 1rem;
+  }
+  .small {
+    font-size: 0.857rem;
+  }
+  .segmented {
+    display: flex;
+    flex-wrap: wrap;
+    gap: var(--space-2);
+  }
+  .seg {
+    padding: 7px 14px;
+    border: 1px solid var(--border-strong);
+    border-radius: var(--radius);
+    background: var(--bg);
+    color: var(--muted);
+    cursor: pointer;
+    font-size: 0.929rem;
+  }
+  .seg:hover {
+    color: var(--text);
+    border-color: var(--faint);
+  }
+  .seg.active {
+    background: var(--accent);
+    border-color: var(--accent);
+    color: var(--accent-text);
+    font-weight: 500;
+  }
+  .preview-heading {
+    margin-bottom: var(--space-3);
+  }
+  .preview {
+    display: grid;
+    grid-auto-flow: column;
+    grid-auto-columns: var(--card-w);
+    gap: var(--space-4);
+    overflow-x: auto;
+    padding-bottom: var(--space-2);
+  }
+  .mock {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-2);
+  }
+  .mock-cover {
+    aspect-ratio: 2 / 3;
+    border-radius: var(--radius-cover);
+    background: linear-gradient(150deg, var(--surface-2), var(--surface-3));
+    display: grid;
+    place-items: center;
+    font-size: 2.4rem;
+    font-weight: 700;
+    color: var(--faint);
+    box-shadow: var(--shadow-cover);
+  }
+  .mock-cover.alt {
+    background: linear-gradient(150deg, color-mix(in srgb, var(--accent) 40%, var(--surface-2)), var(--surface-3));
+  }
+  .mock-cover.alt2 {
+    background: linear-gradient(150deg, #b23b3b, var(--surface-3));
+  }
+  .mock-title {
+    font-size: 0.929rem;
+    font-weight: 500;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+  }
+  .mock-sub {
+    font-size: 0.821rem;
+    color: var(--faint);
+  }
+  .sample {
+    margin: var(--space-4) 0 0;
+    max-width: 60ch;
+    line-height: 1.6;
+  }
+</style>
diff --git a/web/src/lib/components/Shelf.svelte b/web/src/lib/components/Shelf.svelte
index 4cdb1a8..f6b91bc 100644
--- a/web/src/lib/components/Shelf.svelte
+++ b/web/src/lib/components/Shelf.svelte
@@ -52,13 +52,13 @@
     margin-bottom: var(--space-3);
   }
   h2 {
-    font-size: 17px;
+    font-size: 1.214rem;
   }
   .see-all {
     border: none;
     background: transparent;
     color: var(--muted);
-    font-size: 13px;
+    font-size: .929rem;
     cursor: pointer;
     padding: 0;
   }
@@ -68,7 +68,7 @@
   .row {
     display: grid;
     grid-auto-flow: column;
-    grid-auto-columns: 150px;
+    grid-auto-columns: var(--card-w);
     gap: var(--space-4);
     overflow-x: auto;
     padding-bottom: var(--space-2);
@@ -79,7 +79,7 @@
   }
   @media (max-width: 700px) {
     .row {
-      grid-auto-columns: 120px;
+      grid-auto-columns: calc(var(--card-w) * 0.8);
     }
   }
 </style>
diff --git a/web/src/lib/components/Shell.svelte b/web/src/lib/components/Shell.svelte
index a2fd6ca..1b3ca19 100644
--- a/web/src/lib/components/Shell.svelte
+++ b/web/src/lib/components/Shell.svelte
@@ -8,6 +8,7 @@
   import SearchResults from './SearchResults.svelte'
   import Libraries from './Libraries.svelte'
   import Users from './Users.svelte'
+  import Settings from './Settings.svelte'
 
   let searchBox = $state('')
 
@@ -38,6 +39,8 @@
         return 'Libraries'
       case 'users':
         return 'Users'
+      case 'settings':
+        return 'Appearance'
     }
   }
 </script>
@@ -66,6 +69,9 @@
       <button class="navlink" class:active={$view.name === 'browse' && !$view.kind} onclick={() => go({ name: 'browse' })}>
         <span>Browse all</span>
       </button>
+      <button class="navlink" class:active={$view.name === 'settings'} onclick={() => go({ name: 'settings' })}>
+        <span>Appearance</span>
+      </button>
     </nav>
 
     {#if $user?.is_admin}
@@ -125,6 +131,8 @@
         <Libraries />
       {:else if $view.name === 'users'}
         <Users />
+      {:else if $view.name === 'settings'}
+        <Settings />
       {/if}
     </div>
   </main>
@@ -154,7 +162,7 @@
     background: transparent;
     color: var(--text);
     cursor: pointer;
-    font-size: 15px;
+    font-size: 1.071rem;
   }
   .mark {
     display: grid;
@@ -164,7 +172,7 @@
     border-radius: 7px;
     background: var(--accent);
     color: var(--accent-text);
-    font-size: 13px;
+    font-size: .929rem;
     font-weight: 700;
   }
   .links {
@@ -184,7 +192,7 @@
     color: var(--muted);
     text-align: left;
     cursor: pointer;
-    font-size: 13.5px;
+    font-size: .964rem;
   }
   .navlink:hover {
     background: var(--surface-2);
@@ -196,13 +204,13 @@
     font-weight: 500;
   }
   .count {
-    font-size: 12px;
+    font-size: .857rem;
     color: var(--faint);
     font-variant-numeric: tabular-nums;
   }
   .section {
     margin: 0 var(--space-2) -8px;
-    font-size: 11px;
+    font-size: .786rem;
     text-transform: uppercase;
     letter-spacing: 0.07em;
     color: var(--faint);
@@ -228,7 +236,7 @@
     height: 28px;
     border-radius: 50%;
     background: var(--surface-3);
-    font-size: 12px;
+    font-size: .857rem;
     font-weight: 600;
     flex: none;
   }
@@ -239,13 +247,13 @@
     min-width: 0;
   }
   .who strong {
-    font-size: 13px;
+    font-size: .929rem;
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
   }
   .who .faint {
-    font-size: 11px;
+    font-size: .786rem;
   }
   .main {
     display: flex;
@@ -274,7 +282,7 @@
     height: 34px;
     border-radius: 50%;
     cursor: pointer;
-    font-size: 16px;
+    font-size: 1.143rem;
     line-height: 1;
   }
   .back:hover {
diff --git a/web/src/lib/components/Users.svelte b/web/src/lib/components/Users.svelte
index 8cb2ed4..3ada004 100644
--- a/web/src/lib/components/Users.svelte
+++ b/web/src/lib/components/Users.svelte
@@ -204,7 +204,7 @@
     flex: 1;
   }
   .id .muted {
-    font-size: 12px;
+    font-size: .857rem;
   }
   .grants {
     padding: 0 var(--space-4) var(--space-4);
@@ -214,7 +214,7 @@
   }
   .note {
     margin: 0;
-    font-size: 12px;
+    font-size: .857rem;
   }
   .grantrow {
     display: flex;
@@ -223,10 +223,10 @@
   }
   .libname {
     flex: 1;
-    font-size: 13px;
+    font-size: .929rem;
   }
   .libname .faint {
-    font-size: 11px;
+    font-size: .786rem;
     text-transform: uppercase;
     letter-spacing: 0.04em;
   }
@@ -240,7 +240,7 @@
     display: flex;
     align-items: center;
     gap: 6px;
-    font-size: 13px;
+    font-size: .929rem;
     color: var(--text-muted);
     white-space: nowrap;
   }
diff --git a/web/src/lib/nav.ts b/web/src/lib/nav.ts
index 08c496e..f0f1584 100644
--- a/web/src/lib/nav.ts
+++ b/web/src/lib/nav.ts
@@ -9,6 +9,7 @@ export type View =
   | { name: 'search'; query: string }
   | { name: 'libraries' }
   | { name: 'users' }
+  | { name: 'settings' }
 
 export const view = writable<View>({ name: 'home' })
 
diff --git a/web/src/lib/settings.ts b/web/src/lib/settings.ts
new file mode 100644
index 0000000..fa2ce92
--- /dev/null
+++ b/web/src/lib/settings.ts
@@ -0,0 +1,79 @@
+import { writable } from 'svelte/store'
+
+// Display preferences. These are per-device, not per-account: a TV across the
+// room wants bigger text than a laptop, and the same person uses both. Stored
+// in localStorage so a change is instant and needs no round trip.
+
+export interface UiSettings {
+  /** Multiplier on the 15px root size; scales all text. */
+  textScale: number
+  /** Multiplier on cover width in shelves and grids. */
+  cardScale: number
+}
+
+export const DEFAULTS: UiSettings = { textScale: 1, cardScale: 1 }
+
+export const TEXT_STEPS = [
+  { label: 'Small', value: 0.9 },
+  { label: 'Default', value: 1 },
+  { label: 'Large', value: 1.12 },
+  { label: 'Larger', value: 1.28 },
+]
+
+export const CARD_STEPS = [
+  { label: 'Compact', value: 0.85 },
+  { label: 'Default', value: 1 },
+  { label: 'Large', value: 1.2 },
+  { label: 'Extra large', value: 1.45 },
+]
+
+const KEY = 'vellum.ui.settings'
+
+function read(): UiSettings {
+  try {
+    const raw = localStorage.getItem(KEY)
+    if (!raw) return DEFAULTS
+    const parsed = JSON.parse(raw) as Partial<UiSettings>
+    return {
+      textScale: clamp(parsed.textScale ?? DEFAULTS.textScale, 0.8, 1.6),
+      cardScale: clamp(parsed.cardScale ?? DEFAULTS.cardScale, 0.7, 1.8),
+    }
+  } catch {
+    return DEFAULTS
+  }
+}
+
+function clamp(n: number, lo: number, hi: number): number {
+  if (!Number.isFinite(n)) return 1
+  return Math.min(Math.max(n, lo), hi)
+}
+
+/** Apply the settings to the document as CSS variables. */
+export function applySettings(s: UiSettings) {
+  const root = document.documentElement
+  root.style.setProperty('--ui-scale', String(s.textScale))
+  root.style.setProperty('--card-scale', String(s.cardScale))
+}
+
+export const settings = writable<UiSettings>(read())
+
+/** Update one or more settings, persist them, and apply them immediately. */
+export function setSettings(patch: Partial<UiSettings>) {
+  settings.update((current) => {
+    const next = { ...current, ...patch }
+    applySettings(next)
+    try {
+      localStorage.setItem(KEY, JSON.stringify(next))
+    } catch {
+      // Private browsing or a full quota: keep the change for this session.
+    }
+    return next
+  })
+}
+
+export function resetSettings() {
+  setSettings(DEFAULTS)
+}
+
+// Apply whatever was stored before the first paint.
+applySettings(read())