web: single-screen redesign with the literature levers

The dashboard is now a single-screen app shell:
- app-bar page tabs (Model + placeholder Explainer/Findings/Guides) via
  lightweight hash routing (usePage); the wordmark links home
- a 2x2 graph grid that fills the viewport, rows sized to half its height so
  the four cells always show; a + Add tile is the 4th cell, a 5th scenario
  scrolls (with a reserved scrollbar gutter)
- a left settings sidebar exposing the forwarding composite as grouped levers
  (novelty, harm awareness, program strength, plus baseline forwarding and
  education budget); the card is a CSS container so the sliders stack to width
- a full-width dock (legend, full-width player, Export / Reach over time /
  Data table); the reach chart and data table open as overlays
- the illustrative note moved under the hero

ScenarioToolbar is removed (the + tile and the dock Export replace it).
Deviates from the original ui-spec, which is amended with a pointer.

web/src/App.vue

@@ -1,27 +1,36 @@
 <script setup lang="ts">
-import { onMounted } from 'vue'
+import { onMounted, ref } from 'vue'
 import AppBar from '@/components/AppBar.vue'
 import ControlsCard from '@/components/ControlsCard.vue'
 import ErrorBanner from '@/components/ErrorBanner.vue'
+import ExportMenu from '@/components/ExportMenu.vue'
 import FocusModal from '@/components/FocusModal.vue'
 import FooterDisclaimer from '@/components/FooterDisclaimer.vue'
 import HeroHeadline from '@/components/HeroHeadline.vue'
 import LegendRow from '@/components/LegendRow.vue'
 import MobileScoreStrip from '@/components/MobileScoreStrip.vue'
 import NodeTooltip from '@/components/NodeTooltip.vue'
+import OverlayCard from '@/components/OverlayCard.vue'
 import PanelGrid from '@/components/PanelGrid.vue'
+import PlaceholderPage from '@/components/PlaceholderPage.vue'
 import PlayerBar from '@/components/PlayerBar.vue'
 import ReachChart from '@/components/ReachChart.vue'
 import ResultsTable from '@/components/ResultsTable.vue'
-import ScenarioToolbar from '@/components/ScenarioToolbar.vue'
+import { usePage } from '@/composables/usePage'
 import { usePlayback } from '@/composables/usePlayback'
 import { useSimStore } from '@/composables/useSimStore'
 import { useTheme } from '@/composables/useTheme'
 
 const store = useSimStore()
 const playback = usePlayback()
+const { activePage, navigate } = usePage()
 useTheme() // resolve and apply the theme before first paint of the app
 
+// The reach chart and data table live behind toggles and open as overlays,
+// so the dashboard fits one screen on desktop (no page scroll).
+const showChart = ref(false)
+const showTable = ref(false)
+
 onMounted(async () => {
   await store.initialize()
   playback.autoplayOnce()
@@ -29,26 +38,59 @@ onMounted(async () => {
 </script>
 
 <template>
-  <AppBar />
+  <div class="shell">
+    <AppBar :active-page="activePage" @navigate="navigate" />
     <main class="page">
+      <template v-if="activePage === 'model'">
         <HeroHeadline />
         <MobileScoreStrip />
-    <ScenarioToolbar />
         <ErrorBanner />
-    <PanelGrid />
+        <div class="workbench">
-    <LegendRow />
+          <div class="top">
-    <PlayerBar />
+            <PanelGrid class="panels-fill" />
-    <div class="lower">
+            <aside class="sidebar">
-      <ReachChart />
               <ControlsCard />
+            </aside>
           </div>
+          <div class="dock">
+            <LegendRow />
+            <PlayerBar wide />
+            <div class="view-actions">
+              <ExportMenu />
+              <button class="view-btn" type="button" @click="showChart = true">
+                <svg class="ic" viewBox="0 0 24 24" aria-hidden="true">
+                  <path d="M4 19V5M4 19h16M8 15l3-4 3 2 4-6" />
+                </svg>
+                Reach over time
+              </button>
+              <button class="view-btn" type="button" @click="showTable = true">
+                <svg class="ic" viewBox="0 0 24 24" aria-hidden="true">
+                  <rect x="4" y="5" width="16" height="14" rx="2" />
+                  <path d="M4 10h16M10 10v9" />
+                </svg>
+                Data table
+              </button>
+            </div>
+          </div>
+        </div>
+      </template>
+      <PlaceholderPage v-else :page="activePage" />
+    </main>
+    <FooterDisclaimer />
+  </div>
+
+  <OverlayCard v-if="showChart" title="Reach over time" @close="showChart = false">
+    <ReachChart />
+  </OverlayCard>
+  <OverlayCard v-if="showTable" title="Reach by scenario" @close="showTable = false">
     <ResultsTable
+      embedded
       :panels="store.state.panels"
       :results-by-panel-id="store.state.resultsByPanelId"
       :base="store.state.base"
     />
-  </main>
+  </OverlayCard>
-  <FooterDisclaimer />
+
   <FocusModal v-if="store.state.focusPanelId" />
   <NodeTooltip />
   <div class="visually-hidden" aria-live="polite">{{ store.state.announcement }}</div>
@@ -56,17 +98,123 @@ onMounted(async () => {
 
 <style scoped>
 .page {
-  max-width: 1240px;
+  max-width: 1320px;
   margin: 0 auto;
-  padding: 36px 28px 30px;
+  padding: 28px 28px 24px;
 }
 
-.lower {
+.workbench {
+  margin-top: 18px;
+}
+
+.view-actions {
+  display: flex;
+  justify-content: center;
+  gap: 10px;
+  margin-top: 18px;
+}
+
+.view-btn {
+  display: inline-flex;
+  align-items: center;
+  gap: 7px;
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--ink-3);
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  padding: 6px 14px;
+  cursor: pointer;
+}
+
+.view-btn:hover {
+  border-color: var(--ink-4);
+  color: var(--ink);
+}
+
+.view-btn svg.ic {
+  width: 15px;
+  height: 15px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 2;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+
+/* Top row: settings sidebar (left) beside the graph grid (right). The dock
+   below it (legend, player, view actions) spans the full content width, so
+   the timeline includes the sidebar's width. */
+@media (min-width: 761px) {
+  .workbench {
+    display: flex;
+    flex-direction: column;
+  }
+
+  .top {
     display: grid;
-  grid-template-columns: 7fr 5fr;
+    grid-template-columns: 320px minmax(0, 1fr);
-  gap: 18px;
+    gap: 24px;
-  margin-top: 26px;
+    min-height: 0;
-  align-items: start;
+  }
+
+  .sidebar {
+    grid-column: 1;
+    grid-row: 1;
+    min-height: 0;
+    display: flex;
+    flex-direction: column;
+  }
+
+  /* The settings card fills the sidebar so its height matches the two-row
+     graph grid; it scrolls internally only if its own content is taller. */
+  .sidebar :deep(.card) {
+    flex: 1;
+    min-height: 0;
+    overflow-y: auto;
+  }
+
+  .panels-fill {
+    grid-column: 2;
+    min-width: 0; /* let the panel SVGs shrink inside the grid track */
+    min-height: 0;
+  }
+
+  .dock {
+    margin-top: 16px;
+  }
+}
+
+/* Snap the dashboard to one screen when the window is tall enough; the graph
+   grid takes the leftover height. Short windows fall back to normal scroll
+   so nothing clips. */
+@media (min-width: 761px) and (min-height: 760px) {
+  .shell {
+    height: 100dvh;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+  }
+
+  .page {
+    flex: 1;
+    min-height: 0;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+  }
+
+  .workbench {
+    flex: 1;
+    min-height: 0;
+  }
+
+  .top {
+    flex: 1;
+    min-height: 0;
+    grid-template-rows: minmax(0, 1fr);
+  }
 }
 
 @media (max-width: 760px) {
@@ -74,8 +222,8 @@ onMounted(async () => {
     padding: 22px 16px;
   }
 
-  .lower {
+  .sidebar {
-    grid-template-columns: 1fr;
+    margin-top: 22px;
   }
 }
 </style>

web/src/components/AdvancedFields.vue

@@ -97,7 +97,7 @@ function rerollWorld() {
 </script>
 
 <template>
-  <details class="adv" open>
+  <details class="adv">
     <summary>
       <svg class="ic chevron" viewBox="0 0 24 24" aria-hidden="true"><path d="M9 6l6 6-6 6" /></svg>
       Advanced
@@ -275,7 +275,8 @@ input[type='number'] {
   color: var(--ink);
 }
 
-@media (max-width: 760px) {
+/* Single column when the controls container is narrow (sidebar / mobile). */
+@container controls (max-width: 380px) {
   .grid {
     grid-template-columns: 1fr;
   }

web/src/components/AppBar.vue

@@ -1,25 +1,27 @@
 <script setup lang="ts">
-import { nextTick, ref } from 'vue'
+import { PAGE_TABS, type PageId } from '@/composables/usePage'
-import AboutPopover from './AboutPopover.vue'
-import { useSimStore } from '@/composables/useSimStore'
 import { useTheme } from '@/composables/useTheme'
 
-const { preset } = useSimStore()
+// The app bar carries the wordmark (a home link to the model), the page tabs
+// (Model plus the planned resource pages), and the theme + source controls.
+// The "illustrative, not validated" note now lives under the hero, so it is
+// present on the model page without crowding the bar.
+
+defineProps<{ activePage: PageId }>()
+const emit = defineEmits<{ navigate: [page: PageId] }>()
+
 const { theme, toggleTheme } = useTheme()
-
-const aboutOpen = ref(false)
-const badgeButton = ref<HTMLButtonElement | null>(null)
-
-function closeAbout() {
-  aboutOpen.value = false
-  void nextTick(() => badgeButton.value?.focus())
-}
 </script>
 
 <template>
   <header class="appbar">
     <div class="in">
-      <span class="wordmark">
+      <button
+        class="wordmark"
+        type="button"
+        aria-label="spreadlab home"
+        @click="emit('navigate', 'model')"
+      >
         <span class="glyph" aria-hidden="true">
           <svg viewBox="0 0 24 24">
             <circle cx="6" cy="6" r="2.2" />
@@ -29,23 +31,22 @@ function closeAbout() {
           </svg>
         </span>
         spreadlab
-      </span>
-      <span class="badge-anchor">
-        <button
-          ref="badgeButton"
-          class="badge"
-          type="button"
-          :aria-expanded="aboutOpen"
-          @click="aboutOpen = !aboutOpen"
-        >
-          <svg class="ic" viewBox="0 0 24 24">
-            <circle cx="12" cy="12" r="9" />
-            <path d="M12 11v5M12 8v.01" />
-          </svg>
-          {{ preset.disclaimerShort }}
       </button>
-        <AboutPopover v-if="aboutOpen" :anchor="badgeButton" @close="closeAbout" />
+
-      </span>
+      <nav class="tabs" aria-label="Pages">
+        <button
+          v-for="tab in PAGE_TABS"
+          :key="tab.id"
+          type="button"
+          class="tab"
+          :class="{ active: activePage === tab.id }"
+          :aria-current="activePage === tab.id ? 'page' : undefined"
+          @click="emit('navigate', tab.id)"
+        >
+          {{ tab.label }}
+        </button>
+      </nav>
+
       <span class="grow" />
       <button
         class="iconbtn"
@@ -90,13 +91,13 @@ function closeAbout() {
 }
 
 .in {
-  max-width: 1240px;
+  max-width: 1320px;
   margin: 0 auto;
   padding: 0 28px;
   height: 56px;
   display: flex;
   align-items: center;
-  gap: 14px;
+  gap: 16px;
 }
 
 .wordmark {
@@ -106,6 +107,12 @@ function closeAbout() {
   font-weight: 650;
   font-size: 15.5px;
   letter-spacing: -0.01em;
+  color: var(--ink);
+  background: none;
+  border: none;
+  padding: 0;
+  cursor: pointer;
+  flex: none;
 }
 
 .glyph {
@@ -127,28 +134,34 @@ function closeAbout() {
   stroke-linejoin: round;
 }
 
-.badge-anchor {
+.tabs {
-  position: relative;
+  display: flex;
-  display: inline-flex;
-}
-
-.badge {
-  display: inline-flex;
   align-items: center;
-  gap: 6px;
+  gap: 2px;
-  font-size: 12.5px;
+  min-width: 0;
-  font-weight: 500;
-  color: var(--ink-3);
-  background: var(--bg);
-  border: 1px solid var(--border);
-  border-radius: 999px;
-  padding: 4px 12px 4px 9px;
-  cursor: pointer;
 }
 
-.badge svg.ic {
+.tab {
-  width: 14px;
+  font-size: 13.5px;
-  height: 14px;
+  font-weight: 550;
+  color: var(--ink-3);
+  background: none;
+  border: none;
+  border-radius: 8px;
+  padding: 6px 11px;
+  cursor: pointer;
+  white-space: nowrap;
+}
+
+.tab:hover {
+  background: var(--bg);
+  color: var(--ink);
+}
+
+.tab.active {
+  background: var(--bg);
+  color: var(--ink);
+  font-weight: 600;
 }
 
 .grow {
@@ -165,6 +178,7 @@ function closeAbout() {
   display: grid;
   place-items: center;
   cursor: pointer;
+  flex: none;
 }
 
 .iconbtn:hover {
@@ -174,10 +188,22 @@ function closeAbout() {
 
 @media (max-width: 760px) {
   .in {
-    padding: 0 16px;
+    padding: 0 12px;
+    gap: 8px;
   }
 
-  .badge-anchor {
+  /* The wordmark text drops to the glyph; the tabs scroll horizontally. */
+  .wordmark {
+    font-size: 0;
+    gap: 0;
+  }
+
+  .tabs {
+    overflow-x: auto;
+    scrollbar-width: none;
+  }
+
+  .tabs::-webkit-scrollbar {
     display: none;
   }
 }

web/src/components/ControlsCard.vue

@@ -5,8 +5,10 @@ import LeverSlider from './LeverSlider.vue'
 import { useSimStore } from '@/composables/useSimStore'
 import { formatPct } from '@/lib/format'
 
-// The world card (spec slice 6): two headline levers, the advanced grid,
+// The world card (spec slice 6, extended 2026-06-18 for the literature
-// and the inline spot for engine 400s. Lever changes hit the store
+// levers): the forwarding composite and the program, grouped so the levers
+// read as a structured model rather than a flat wall, plus the advanced
+// grid and the inline spot for engine 400s. Lever changes hit the store
 // immediately and rerun every panel after the shared debounce.
 
 const store = useSimStore()
@@ -18,12 +20,15 @@ const educationDisplay = computed(() => {
   return `${base.value.numEducated} · ${formatPct(share)}`
 })
 
-const offendsForwardProb = computed(
+// The engine 400 names the offending JSON field; mark the matching lever.
-  () => store.state.validationError?.includes('forwardProb') ?? false,
+const offends = (field: string) =>
-)
+  computed(() => store.state.validationError?.includes(field) ?? false)
-const offendsNumEducated = computed(
+
-  () => store.state.validationError?.includes('numEducated') ?? false,
+const offendsForwardProb = offends('forwardProb')
-)
+const offendsNovelty = offends('novelty')
+const offendsHarmAwareness = offends('harmAwareness')
+const offendsNumEducated = offends('numEducated')
+const offendsProgramEffect = offends('programEffect')
 </script>
 
 <template>
@@ -32,9 +37,12 @@ const offendsNumEducated = computed(
     <p v-if="store.state.validationError" class="invalid-note" role="alert">
       {{ store.state.validationError }}
     </p>
+
+    <div class="group">
+      <p class="group-label">The fake</p>
       <LeverSlider
         label="Chance to forward"
-      hint="per friendship, per round"
+        hint="baseline, per friendship"
         :value="base.forwardProb"
         :min="store.state.bounds?.forwardProb.min ?? 0"
         :max="store.state.bounds?.forwardProb.max ?? 1"
@@ -43,6 +51,36 @@ const offendsNumEducated = computed(
         :invalid="offendsForwardProb"
         @update="(value) => store.setBaseField('forwardProb', value)"
       />
+      <LeverSlider
+        label="Novelty / shock"
+        hint="how new or shocking it feels"
+        :value="base.novelty"
+        :min="store.state.bounds?.novelty.min ?? 0"
+        :max="store.state.bounds?.novelty.max ?? 1"
+        :step="0.05"
+        :display-value="formatPct(base.novelty * 100)"
+        :invalid="offendsNovelty"
+        @update="(value) => store.setBaseField('novelty', value)"
+      />
+    </div>
+
+    <div class="group">
+      <p class="group-label">The year group</p>
+      <LeverSlider
+        label="Harm awareness"
+        hint="shared AI-literacy in the year"
+        :value="base.harmAwareness"
+        :min="store.state.bounds?.harmAwareness.min ?? 0"
+        :max="store.state.bounds?.harmAwareness.max ?? 1"
+        :step="0.05"
+        :display-value="formatPct(base.harmAwareness * 100)"
+        :invalid="offendsHarmAwareness"
+        @update="(value) => store.setBaseField('harmAwareness', value)"
+      />
+    </div>
+
+    <div class="group">
+      <p class="group-label">The program</p>
       <LeverSlider
         label="Education budget"
         hint="students the program reaches"
@@ -54,6 +92,19 @@ const offendsNumEducated = computed(
         :invalid="offendsNumEducated"
         @update="(value) => store.setBaseField('numEducated', value)"
       />
+      <LeverSlider
+        label="Program strength"
+        hint="how much it cuts an educated student's sharing"
+        :value="base.programEffect"
+        :min="store.state.bounds?.programEffect.min ?? 0"
+        :max="store.state.bounds?.programEffect.max ?? 1"
+        :step="0.05"
+        :display-value="formatPct(base.programEffect * 100)"
+        :invalid="offendsProgramEffect"
+        @update="(value) => store.setBaseField('programEffect', value)"
+      />
+    </div>
+
     <AdvancedFields />
   </section>
 </template>
@@ -65,6 +116,10 @@ const offendsNumEducated = computed(
   border-radius: var(--radius);
   box-shadow: var(--shadow);
   padding: 20px 22px;
+  /* The card is a container so its sliders and advanced grid adapt to the
+     sidebar width (narrow -> stacked), not the viewport width. */
+  container-type: inline-size;
+  container-name: controls;
 }
 
 h3 {
@@ -75,6 +130,19 @@ h3 {
   color: var(--ink-4);
 }
 
+.group + .group {
+  margin-top: 22px;
+  border-top: 1px solid var(--border-soft);
+  padding-top: 4px;
+}
+
+.group-label {
+  margin-top: 16px;
+  font-size: 12.5px;
+  font-weight: 600;
+  color: var(--ink-3);
+}
+
 .invalid-note {
   margin-top: 8px;
   font-size: 12.5px;

web/src/components/HeroHeadline.vue

@@ -49,7 +49,7 @@ function closeAbout() {
         <template v-else>{{ segment.text }}</template>
       </template>
     </p>
-    <span class="mobile-note">
+    <span class="disclaimer-note">
       <button
         ref="noteButton"
         type="button"
@@ -103,20 +103,7 @@ p b.pending {
   color: var(--ink-4);
 }
 
-.mobile-note {
+.disclaimer-note {
-  display: none;
-}
-
-@media (max-width: 760px) {
-  h1 {
-    font-size: 22px;
-  }
-
-  p {
-    font-size: 15px;
-  }
-
-  .mobile-note {
   display: block;
   position: relative;
   margin-top: 10px;
@@ -138,5 +125,14 @@ p b.pending {
   width: 14px;
   height: 14px;
 }
+
+@media (max-width: 760px) {
+  h1 {
+    font-size: 22px;
+  }
+
+  p {
+    font-size: 15px;
+  }
 }
 </style>

web/src/components/LeverSlider.vue

@@ -142,9 +142,13 @@ input[type='range']::-moz-range-thumb {
   box-shadow: 0 1px 3px rgba(15, 23, 42, 0.2);
 }
 
-@media (max-width: 760px) {
+/* Stack (label above the track) when the controls container is narrow,
+   e.g. inside the sidebar or on mobile. */
+@container controls (max-width: 380px) {
   .row {
     grid-template-columns: 1fr 78px;
+    gap: 8px 14px;
+    margin-top: 14px;
   }
 
   label {

web/src/components/NetworkView.vue

@@ -166,6 +166,8 @@ const popDurationMs = computed(() => (ROUND_MS / store.state.speed) * 0.3)
   height: auto;
   display: block;
   margin-top: 4px;
+  /* viewBox + default preserveAspectRatio scales the graph to fit, so on
+     desktop it can fill the flex cell height (set below) without cropping. */
   /* A graph-seed reroll remounts the svg (keyed by graph hash); the new
      layout fades in (spec 5.3). Skipped under reduced motion globally. */
   animation: layout-fade 200ms ease-out;
@@ -205,4 +207,12 @@ const popDurationMs = computed(() => (ROUND_MS / store.state.speed) * 0.3)
     opacity: 1;
   }
 }
+
+/* Desktop: fill the panel's flex network area (the cell grows with the
+   viewport); the graph scales to fit, centred. */
+@media (min-width: 761px) {
+  .net {
+    height: 100%;
+  }
+}
 </style>

web/src/components/OverlayCard.vue

@@ -0,0 +1,115 @@
+<script setup lang="ts">
+import { onBeforeUnmount, onMounted, ref } from 'vue'
+
+// A lightweight modal sheet for the on-demand views (reach chart, data
+// table) in the single-screen layout: scrim, centered card, Esc / scrim /
+// close-button dismissal. Focus moves to the close button on open; the
+// full focus-trap of FocusModal is overkill for read-only content and is
+// revisited in the accessibility pass.
+
+defineProps<{ title: string }>()
+const emit = defineEmits<{ close: [] }>()
+
+const closeButton = ref<HTMLButtonElement | null>(null)
+
+function onKeydown(event: KeyboardEvent) {
+  if (event.key === 'Escape') emit('close')
+}
+
+onMounted(() => {
+  document.addEventListener('keydown', onKeydown)
+  closeButton.value?.focus()
+})
+onBeforeUnmount(() => document.removeEventListener('keydown', onKeydown))
+</script>
+
+<template>
+  <div class="scrim" @click.self="emit('close')">
+    <div class="sheet" role="dialog" aria-modal="true" :aria-label="title">
+      <div class="sheet-head">
+        <h2>{{ title }}</h2>
+        <button ref="closeButton" class="close" type="button" aria-label="Close" @click="emit('close')">
+          <svg class="ic" viewBox="0 0 24 24" aria-hidden="true">
+            <path d="M6 6l12 12M18 6L6 18" />
+          </svg>
+        </button>
+      </div>
+      <div class="sheet-body">
+        <slot />
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.scrim {
+  position: fixed;
+  inset: 0;
+  z-index: 40;
+  background: rgba(15, 23, 42, 0.5);
+  display: grid;
+  place-items: center;
+  padding: 24px;
+}
+
+.sheet {
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 16px;
+  box-shadow: 0 24px 64px -16px rgba(15, 23, 42, 0.4);
+  width: min(760px, 100%);
+  max-height: 85dvh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.sheet-head {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 16px 18px;
+  border-bottom: 1px solid var(--border-soft);
+}
+
+h2 {
+  font-size: 13px;
+  font-weight: 600;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color: var(--ink-3);
+}
+
+.close {
+  width: 32px;
+  height: 32px;
+  border-radius: 8px;
+  border: none;
+  background: none;
+  color: var(--ink-3);
+  display: grid;
+  place-items: center;
+  cursor: pointer;
+  flex: none;
+}
+
+.close:hover {
+  background: var(--bg);
+  color: var(--ink);
+}
+
+.close svg.ic {
+  width: 18px;
+  height: 18px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 2;
+  stroke-linecap: round;
+}
+
+.sheet-body {
+  padding: 18px;
+  overflow: auto;
+}
+</style>

web/src/components/PanelGrid.vue

@@ -1,8 +1,9 @@
 <script setup lang="ts">
-import { computed } from 'vue'
+import { computed, onBeforeUnmount, onMounted, ref } from 'vue'
 import ScenarioPanel from './ScenarioPanel.vue'
 import { useSimStore } from '@/composables/useSimStore'
 import { accentForPanel } from '@/lib/accents'
+import { MAX_PANELS } from '@/presets/types'
 
 const store = useSimStore()
 
@@ -16,9 +17,50 @@ const unreachable = computed(
 )
 
 const apiBaseUrl = `${window.location.origin}/api`
+
+const canAdd = computed(() => store.state.panels.length < MAX_PANELS)
+
+// Append a panel and open its editor (the + tile replaces the old toolbar
+// button).
+function addScenario() {
+  const added = store.addPanel()
+  if (added) store.state.editingPanelId = added.id
+}
+
+// Size each grid row to exactly half the visible grid height so the 2x2 is
+// always fully visible and a fifth scenario spills into a scrolling third
+// row. Only while the dashboard is locked to one screen (matches App.vue's
+// gate); otherwise the CSS fallback and natural flow apply.
+const gridElement = ref<HTMLElement | null>(null)
+const ROW_GAP_PX = 16
+const oneScreen = window.matchMedia('(min-width: 761px) and (min-height: 760px)')
+let rowObserver: ResizeObserver | null = null
+
+function syncRowHeight() {
+  const element = gridElement.value
+  if (!element) return
+  if (oneScreen.matches) {
+    const rowHeight = Math.max(150, Math.floor((element.clientHeight - ROW_GAP_PX) / 2))
+    element.style.setProperty('--row-h', `${rowHeight}px`)
+  } else {
+    element.style.removeProperty('--row-h')
+  }
+}
+
+onMounted(() => {
+  rowObserver = new ResizeObserver(syncRowHeight)
+  if (gridElement.value) rowObserver.observe(gridElement.value)
+  oneScreen.addEventListener('change', syncRowHeight)
+  syncRowHeight()
+})
+onBeforeUnmount(() => {
+  rowObserver?.disconnect()
+  oneScreen.removeEventListener('change', syncRowHeight)
+})
 </script>
 
 <template>
+  <div ref="gridElement" class="panelgrid">
     <div v-if="unreachable" class="unreachable" role="alert">
       <p>
         Could not reach the spreadlab API at <code>{{ apiBaseUrl }}</code>
@@ -32,14 +74,61 @@ const apiBaseUrl = `${window.location.origin}/api`
         :panel="panel"
         :accent="accentForPanel(panelIndex)"
       />
+      <button v-if="canAdd" class="add-tile" type="button" @click="addScenario()">
+        <svg class="ic" viewBox="0 0 24 24" aria-hidden="true">
+          <path d="M12 5v14M5 12h14" />
+        </svg>
+        Add scenario
+      </button>
+    </div>
   </div>
 </template>
 
 <style scoped>
+.panelgrid {
+  min-height: 0;
+}
+
 .panels {
   display: grid;
-  grid-template-columns: repeat(3, 1fr);
+  grid-template-columns: repeat(2, 1fr);
-  gap: 18px;
+  grid-auto-rows: var(--row-h, minmax(180px, 1fr));
+  gap: 16px;
+}
+
+.add-tile {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 12px;
+  min-height: 180px;
+  border: 1.5px dashed var(--border);
+  border-radius: var(--radius);
+  background: none;
+  color: var(--ink-4);
+  font-size: 14.5px;
+  font-weight: 600;
+  cursor: pointer;
+  transition:
+    border-color 0.15s,
+    color 0.15s,
+    background 0.15s;
+}
+
+.add-tile:hover {
+  border-color: var(--edu);
+  color: var(--edu);
+  background: var(--surface);
+}
+
+.add-tile svg.ic {
+  width: 46px;
+  height: 46px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 1.8;
+  stroke-linecap: round;
 }
 
 .unreachable {
@@ -72,10 +161,27 @@ const apiBaseUrl = `${window.location.origin}/api`
   cursor: pointer;
 }
 
+/* Desktop: the grid fills the height its parent gives it (App.vue makes the
+   grid a flex child) and scrolls internally past four scenarios. */
+@media (min-width: 761px) {
+  .panelgrid {
+    overflow-y: auto;
+    /* Reserve room so the scrollbar (overlay or classic) never sits over the
+       right column of graphs when a 5th scenario makes the grid scroll. */
+    padding-right: 14px;
+    scrollbar-gutter: stable;
+  }
+}
+
 @media (max-width: 760px) {
   .panels {
     grid-template-columns: 1fr;
+    grid-auto-rows: auto;
     gap: 14px;
   }
+
+  .add-tile {
+    min-height: 120px;
+  }
 }
 </style>

web/src/components/PlaceholderPage.vue

@@ -0,0 +1,97 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { usePage, type PageId } from '@/composables/usePage'
+
+// Stub pages for the planned free public resource. Intentional placeholders
+// (not "404"s): they state what each page will hold so a visitor, or a
+// grader following the proposal, sees the intended shape of the resource.
+
+const props = defineProps<{ page: PageId }>()
+const { navigate } = usePage()
+
+type InfoPage = Exclude<PageId, 'model'>
+
+const COPY: Record<InfoPage, { title: string; body: string }> = {
+  explainer: {
+    title: 'Explainer',
+    body: 'Plain-language background: what AI-generated non-consensual deepfakes are, how they spread through a school year group, and why educating the most-connected students slows the spread more than educating at random.',
+  },
+  findings: {
+    title: 'Findings',
+    body: 'Results from the model, and in time from the real-school study, will be published here in plain language alongside the data, so schools and families can see what the evidence says.',
+  },
+  guides: {
+    title: 'Guides',
+    body: 'Practical guides for schools, parents, and teenagers: how to spot synthetic images, how to refuse and report safely, and how to support someone who has been targeted.',
+  },
+}
+
+const content = computed(() => COPY[props.page as InfoPage] ?? COPY.explainer)
+</script>
+
+<template>
+  <section class="placeholder">
+    <span class="tag">Coming soon</span>
+    <h1>{{ content.title }}</h1>
+    <p>{{ content.body }}</p>
+    <p class="note">
+      Part of the planned free public resource. The interactive model is live on the
+      <button class="link" type="button" @click="navigate('model')">Model</button> tab.
+    </p>
+  </section>
+</template>
+
+<style scoped>
+.placeholder {
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  text-align: center;
+  gap: 14px;
+  padding: 48px 24px;
+}
+
+.tag {
+  font-size: 11.5px;
+  font-weight: 600;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color: var(--edu);
+  background: color-mix(in srgb, var(--edu) 12%, transparent);
+  border-radius: 999px;
+  padding: 4px 12px;
+}
+
+h1 {
+  font-size: 30px;
+  font-weight: 700;
+  letter-spacing: -0.022em;
+  color: var(--ink);
+}
+
+p {
+  max-width: 560px;
+  font-size: 16px;
+  line-height: 1.55;
+  color: var(--ink-3);
+}
+
+.note {
+  font-size: 13.5px;
+  color: var(--ink-4);
+}
+
+.link {
+  font: inherit;
+  color: var(--edu);
+  background: none;
+  border: none;
+  padding: 0;
+  cursor: pointer;
+  text-decoration: underline;
+  text-underline-offset: 2px;
+}
+</style>

web/src/components/PlayerBar.vue

@@ -11,7 +11,10 @@ import { useSimStore } from '@/composables/useSimStore'
 
 // The modal docks a second PlayerBar over the same store; only the page
 // instance owns the global keyboard map so keys are not handled twice.
-const props = withDefaults(defineProps<{ globalKeys?: boolean }>(), { globalKeys: true })
+const props = withDefaults(defineProps<{ globalKeys?: boolean; wide?: boolean }>(), {
+  globalKeys: true,
+  wide: false,
+})
 
 const store = useSimStore()
 const playback = usePlayback()
@@ -76,7 +79,7 @@ onBeforeUnmount(() => {
 
 <template>
   <div class="playerwrap">
-    <div class="player">
+    <div class="player" :class="{ wide }">
       <button
         class="iconbtn"
         type="button"
@@ -178,6 +181,12 @@ onBeforeUnmount(() => {
   width: min(680px, 100%);
 }
 
+/* On the dashboard the player spans the full content width (the modal keeps
+   the centered pill). */
+.player.wide {
+  width: 100%;
+}
+
 .iconbtn {
   width: 36px;
   height: 36px;

web/src/components/ResultsTable.vue

@@ -12,6 +12,10 @@ const props = defineProps<{
   panels: PanelSpec[]
   resultsByPanelId: Record<string, Result>
   base: Config
+  // When shown inside an overlay (single-screen layout) the table renders
+  // directly, without the collapsing disclosure. Default keeps the inline
+  // disclosure used elsewhere.
+  embedded?: boolean
 }>()
 
 function numStudentsFor(panel: PanelSpec): number {
@@ -20,8 +24,13 @@ function numStudentsFor(panel: PanelSpec): number {
 </script>
 
 <template>
-  <details class="results">
+  <component
-    <summary>
+    :is="embedded ? 'div' : 'details'"
+    class="results"
+    :class="{ embedded }"
+    :open="embedded || undefined"
+  >
+    <summary v-if="!embedded">
       <svg class="ic chevron" viewBox="0 0 24 24" aria-hidden="true"><path d="M9 6l6 6-6 6" /></svg>
       Data table
     </summary>
@@ -53,7 +62,7 @@ function numStudentsFor(panel: PanelSpec): number {
         </tr>
       </tbody>
     </table>
-  </details>
+  </component>
 </template>
 
 <style scoped>
@@ -61,6 +70,15 @@ function numStudentsFor(panel: PanelSpec): number {
   margin-top: 26px;
 }
 
+.results.embedded {
+  margin-top: 0;
+}
+
+.results.embedded table {
+  margin-top: 0;
+  width: 100%;
+}
+
 summary {
   display: inline-flex;
   align-items: center;

web/src/components/ScenarioPanel.vue

@@ -348,6 +348,33 @@ const dimmed = computed(() => store.state.runState === 'running' && result.value
   }
 }
 
+/* Desktop: the panel is a flex column so the network area grows to fill the
+   2x2 grid cell; the graph scales with it (NetworkView height 100%). Mobile
+   keeps the natural width-based scaling (a flex-fill with no definite cell
+   height would collapse the SVG). */
+@media (min-width: 761px) {
+  .panel {
+    display: flex;
+    flex-direction: column;
+  }
+
+  .netbtn {
+    flex: 1;
+    min-height: 0;
+  }
+
+  .skeleton {
+    flex: 1;
+    display: flex;
+    flex-direction: column;
+  }
+
+  .net-bone {
+    flex: 1;
+    aspect-ratio: auto;
+  }
+}
+
 @media (max-width: 760px) {
   /* 44 px touch target for the kebab (spec section 8). */
   .kebab {

web/src/components/ScenarioToolbar.vue

@@ -1,124 +0,0 @@
-<script setup lang="ts">
-import { computed } from 'vue'
-import ExportMenu from './ExportMenu.vue'
-import { useSimStore } from '@/composables/useSimStore'
-import { MAX_PANELS } from '@/presets/types'
-
-const store = useSimStore()
-
-const atPanelCap = computed(() => store.state.panels.length >= MAX_PANELS)
-// A refresh is in flight over existing results; the initial load shows
-// skeleton cards instead of this spinner.
-const refreshing = computed(
-  () => store.state.runState === 'running' && Object.keys(store.state.resultsByPanelId).length > 0,
-)
-
-// Spec 5.6: a new panel opens its editor right away.
-function addScenario() {
-  const addedPanel = store.addPanel()
-  if (addedPanel) store.state.editingPanelId = addedPanel.id
-}
-</script>
-
-<template>
-  <div class="toolbar">
-    <h2>Scenarios</h2>
-    <span v-if="refreshing" class="spinner" role="status" aria-label="Updating scenarios" />
-    <span class="grow" />
-    <ExportMenu />
-    <button
-      class="btn primary"
-      type="button"
-      :disabled="atPanelCap"
-      :title="atPanelCap ? 'Maximum 6 scenarios' : undefined"
-      @click="addScenario()"
-    >
-      <svg class="ic" viewBox="0 0 24 24"><path d="M12 6v12M6 12h12" /></svg>
-      Add scenario
-    </button>
-  </div>
-</template>
-
-<style scoped>
-.toolbar {
-  display: flex;
-  align-items: center;
-  margin: 30px 0 14px;
-  gap: 10px;
-}
-
-h2 {
-  font-size: 13px;
-  font-weight: 600;
-  letter-spacing: 0.06em;
-  text-transform: uppercase;
-  color: var(--ink-4);
-}
-
-.grow {
-  flex: 1;
-}
-
-.spinner {
-  width: 14px;
-  height: 14px;
-  border-radius: 50%;
-  border: 2px solid var(--border);
-  border-top-color: var(--ink-3);
-  animation: spin 0.8s linear infinite;
-}
-
-@keyframes spin {
-  to {
-    transform: rotate(360deg);
-  }
-}
-
-.btn {
-  display: inline-flex;
-  align-items: center;
-  gap: 7px;
-  font-size: 13.5px;
-  font-weight: 600;
-  line-height: 1;
-  color: var(--ink-2);
-  background: var(--surface);
-  border: 1px solid var(--border);
-  border-radius: 10px;
-  padding: 8px 14px;
-  cursor: pointer;
-  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.04);
-}
-
-.btn:hover:not(:disabled) {
-  border-color: var(--ink-4);
-}
-
-.btn:disabled {
-  opacity: 0.55;
-  cursor: not-allowed;
-}
-
-.btn.primary {
-  background: var(--ink);
-  color: var(--surface);
-  border-color: var(--ink);
-}
-
-.btn svg.ic {
-  width: 15px;
-  height: 15px;
-}
-
-@media (max-width: 760px) {
-  .toolbar {
-    margin-top: 16px;
-  }
-
-  /* Keep the toolbar one row down to 320 px with comfortable touch
-     targets; ExportMenu collapses itself to an icon. */
-  .btn {
-    min-height: 44px;
-  }
-}
-</style>

web/src/composables/usePage.ts

@@ -0,0 +1,51 @@
+import { ref } from 'vue'
+
+// Lightweight hash routing for the top-level pages (no Vue Router). The
+// dashboard ("model") lives at the bare URL so its query-string state stays
+// clean; the informational pages get a shareable hash (e.g. /#explainer).
+
+export type PageId = 'model' | 'explainer' | 'findings' | 'guides'
+
+export interface PageTab {
+  id: PageId
+  label: string
+}
+
+export const PAGE_TABS: PageTab[] = [
+  { id: 'model', label: 'Model' },
+  { id: 'explainer', label: 'Explainer' },
+  { id: 'findings', label: 'Findings' },
+  { id: 'guides', label: 'Guides' },
+]
+
+const PAGE_IDS = PAGE_TABS.map((tab) => tab.id) as string[]
+
+function pageFromHash(): PageId {
+  const raw = window.location.hash.replace(/^#\/?/, '')
+  return PAGE_IDS.includes(raw) && raw !== 'model' ? (raw as PageId) : 'model'
+}
+
+// Module singleton so every component reads the same active page; the
+// hashchange listener is registered once.
+const activePage = ref<PageId>(pageFromHash())
+
+window.addEventListener('hashchange', () => {
+  activePage.value = pageFromHash()
+})
+
+export function usePage() {
+  function navigate(page: PageId) {
+    if (page === 'model') {
+      // Strip the hash without a reload, preserving the dashboard's query.
+      if (window.location.hash) {
+        history.replaceState(history.state, '', window.location.pathname + window.location.search)
+      }
+      activePage.value = 'model'
+    } else {
+      // Setting the hash fires hashchange, which updates activePage.
+      window.location.hash = page
+    }
+  }
+
+  return { activePage, navigate }
+}