diff --git a/package.json b/package.json
index 393ad00..8dfde0b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "vaxviz",
-  "version": "0.0.0",
+  "version": "0.1.0",
   "private": true,
   "type": "module",
   "engines": {
diff --git a/src/App.vue b/src/App.vue
index 96a780f..ab6aafe 100644
--- a/src/App.vue
+++ b/src/App.vue
@@ -1,20 +1,38 @@
+<template>
+  <AppHeader />
+  <main class="flex">
+    <PlotControls />
+    <div class="flex flex-col w-full h-full max-w-full max-h-full gap-y-5">
+      <RidgelinePlot />
+      <ColorLegend />
+    </div>
+  </main>
+</template>
+
 <script setup lang="ts">
+import AppHeader from './components/AppHeader.vue';
 import PlotControls from './components/PlotControls.vue';
 import ColorLegend from './components/ColorLegend.vue';
 import RidgelinePlot from './components/RidgelinePlot.vue';
 </script>
 
-<template>
-  <div class="flex h-screen max-h-screen">
-    <div class="flex h-full max-h-full flex-col justify-start gap-y-5">
-      <PlotControls />
-      <div class="w-75 m-5">
-        <ColorLegend />
-      </div>
-    </div>
-    <RidgelinePlot />
-  </div>
-</template>
+<style lang="scss">
+$header-padding: calc(var(--spacing)* 5);
+$logo-height: calc(var(--spacing)* 20);
+
+header {
+  padding: $header-padding;
+  margin-bottom: $header-padding;
+
+  img#logo {
+    height: $logo-height;
+  }
+}
+
+main {
+  $header-height: calc(#{$logo-height} + (#{$header-padding} * 3));
 
-<style scoped>
+  height: calc(100vh - #{$header-height});
+  max-height: calc(100vh - #{$header-height});
+}
 </style>
diff --git a/src/assets/styles/main.css b/src/assets/styles/main.css
index c751084..ba0dcca 100644
--- a/src/assets/styles/main.css
+++ b/src/assets/styles/main.css
@@ -50,3 +50,12 @@
   right: 100px;
   width: max-content;
 }
+
+a, button.link {
+  color: var(--color-fg-brand);
+  text-decoration: underline;
+}
+
+button {
+  cursor: pointer;
+}
diff --git a/src/components/AppHeader.vue b/src/components/AppHeader.vue
new file mode 100644
index 0000000..6f047f1
--- /dev/null
+++ b/src/components/AppHeader.vue
@@ -0,0 +1,82 @@
+<template>
+  <header class="border-b border-gray-300 flex items-center justify-between">
+    <div class="flex flex-col gap-2">
+      <a href="https://www.vaccineimpact.org/" target="_blank">
+        <img src="/logo.png" id="logo" alt="VIMC logo" />
+      </a>
+    </div>
+    <FwbAlert
+      type="danger"
+      class="border-t-4 rounded-none"
+    >
+      <template #icon>
+        <img class="w-4 h-4 mr-2" src="@/assets/images/icons/dangerInfoIcon.svg" alt=""/>
+        <span class="sr-only">Error</span>
+      </template>
+      <template #title>
+        <h3 class="text-lg font-medium">
+          Provisional estimates. Not to be forwarded or cited.
+        </h3>
+      </template>
+      <template #default>
+        <p class="mt-2">This is a preview. All estimates shown are representative only. Do not use or forward them.</p>
+      </template>
+    </FwbAlert>
+    <div class="flex flex-col gap-4 items-end">
+      <!-- TODO: When paper is published, add the link, and remove 'forthcoming'. -->
+      <p class="text-right">This visualization tool accompanies Gaythorpe et al. (forthcoming)</p>
+      <button
+        id="aboutLink"
+        @click="aboutModalVisible = true"
+        href="#"
+        class="link"
+      >
+        About
+      </button>
+    </div>
+  </header>
+  <FwbModal
+    v-if="aboutModalVisible"
+    @close="aboutModalVisible = false"
+  >
+    <template #header>
+      <div class="text-lg">
+        About
+      </div>
+    </template>
+    <template #body>
+      <div class="flex flex-col gap-y-4 leading-relaxed">
+        <!-- TODO: When paper is published, add the link and replace '(forthcoming)' with '(2026)'. -->
+        <p>
+          This visualization tool accompanies VIMC's fourth publication, Gaythorpe et al (forthcoming).
+        </p>
+        <!-- TODO: The commented text will be uncommented once the estimates are final / published; until then we have to caveat them. -->
+        <!-- <p>
+          It shows VIMC's estimates of health impact from vaccination against 14 diseases in {{ countryOptions.length }} low- and middle-income countries from 2000 to 2030
+          (2040 for cholera) for the <a href="https://www.gavi.org/" target="_blank">Gavi</a> portfolio of vaccination programmes.
+        </p> -->
+        <!-- NB: The number of diseases is 14 per the paper, and not (necessarily) the length of diseaseOptions.json, which may carve up diseases differently (particularly Meningitis). -->
+        <p>
+          Once that paper is published, this will show VIMC's estimates of health impact from vaccination against 14 diseases in {{ countryOptions.length }} low- and middle-income countries from 2000 to 2030
+          (2040 for cholera) for the <a href="https://www.gavi.org/" target="_blank">Gavi</a> portfolio of vaccination programmes. The numbers shown are only representative, pending publication.
+        </p>
+        <p>
+          Model estimates are presented in terms of 'vaccine impact ratios', defined as deaths or disability-adjusted life years (DALYs) averted per vaccination.
+        </p>
+        <p class="text-xs text-gray-500 mt-2">
+          Vaxviz version: {{ version }}
+        </p>
+      </div>
+    </template>
+  </FwbModal>
+</template>
+
+<script setup lang="ts">
+import { FwbAlert, FwbModal } from 'flowbite-vue';
+import countryOptions from '@/data/options/countryOptions.json';
+import { ref } from 'vue';
+
+import { version } from '@/../package.json';
+
+const aboutModalVisible = ref(false);
+</script>
diff --git a/src/components/ColorLegend.vue b/src/components/ColorLegend.vue
index 1402ded..eb3302c 100644
--- a/src/components/ColorLegend.vue
+++ b/src/components/ColorLegend.vue
@@ -1,17 +1,17 @@
 <template>
   <div
     v-if="colors && colors.length >= 2"
-    class="max-w-full h-full"
+    class="h-20 flex mb-5 w-fit ml-10"
     id="colorLegend"
   >
-    <h3 class="fs-3 font-medium mb-5 text-heading mb-2">
-      Legend
-    </h3>
-    <ul class="flex flex-col gap-y-1 max-h-full max-w-full">
+    <ul
+      class="flex flex-col gap-y-1 flex-wrap max-h-full min-h-0"
+      :style="{ 'margin-left': `${plotLeftMargin}px` }"
+    >
       <li
         v-for="([value, color]) in colors"
         :key="value"
-        class="flex gap-x-2 text-sm"
+        class="flex gap-x-2 text-sm mr-20"
       >
         <span
           class="legend-color-box"
@@ -32,6 +32,7 @@ import { useColorStore } from '@/stores/colorStore';
 import { dimensionOptionLabel } from '@/utils/options';
 import { useAppStore } from '@/stores/appStore';
 import { Axis, Dimension, LocResolution } from '@/types';
+import { margins } from '@/utils/plotConfiguration';
 
 const appStore = useAppStore();
 const colorStore = useColorStore();
@@ -65,6 +66,9 @@ const colorBoxStyle = (color: HEX) => {
     borderColor: strokeColor,
   }
 }
+
+// Align the left edge of the legend with that of the plot.
+const plotLeftMargin = computed(() => margins(appStore.dimensions[Axis.ROW]).left);
 </script>
 
 <style scoped>
diff --git a/src/components/RidgelinePlot.vue b/src/components/RidgelinePlot.vue
index bcd3338..1f448e8 100644
--- a/src/components/RidgelinePlot.vue
+++ b/src/components/RidgelinePlot.vue
@@ -1,5 +1,5 @@
 <template>
-  <div class="chart-container">
+  <div class="chart-container min-h-0 flex-1 flex">
     <FwbSpinner v-if="dataStore.isLoading" class="m-auto" size="8" />
     <FetchErrorAlert v-else-if="dataStore.fetchErrors.length" />
     <p v-else-if="noDataToDisplay" class="m-auto">
@@ -15,6 +15,7 @@
         lineCount: relevantRidgeLines.length,
         ...appStore.dimensions,
       })"
+      class="flex-1 m-10"
     />
   </div>
 </template>
@@ -139,19 +140,3 @@ const updateChart = debounce(() => {
 watch([relevantRidgeLines, () => appStore.focus, chartWrapper], updateChart, { immediate: true });
 </script>
 
-<style lang="scss" scoped>
-.chart-container {
-  --chart-margin: 80px;
-  width: 100%;
-  height: calc(100dvh - 2 * var(--chart-margin));
-  display: flex;
-  flex-wrap: wrap;
-}
-
-#chartWrapper {
-  width: 100%;
-  height: 100%;
-  flex: 1 1 auto;
-  margin: var(--chart-margin);
-}
-</style>
diff --git a/src/utils/plotConfiguration.ts b/src/utils/plotConfiguration.ts
index 8d24ae1..7ae0ce0 100644
--- a/src/utils/plotConfiguration.ts
+++ b/src/utils/plotConfiguration.ts
@@ -116,6 +116,8 @@ const axisConfiguration = (
     }
   ];
 
+export const margins = (rowDimension: Dimension) => ({ left: yAxisNeedsExtraSpace(rowDimension) ? 170 : 110 });
+
 export const plotConfiguration = (
   rowDimension: Dimension,
   logScaleEnabled: boolean,
@@ -128,7 +130,6 @@ export const plotConfiguration = (
 } => {
   const numScales = numericalScales(logScaleEnabled, lines);
   const catScales = categoricalScales(lines);
-  const margins = { left: yAxisNeedsExtraSpace(rowDimension) ? 170 : 110 };
   const tickConfig = tickConfiguration(logScaleEnabled, rowDimension);
   const constructorOptions = {
     tickConfig,
@@ -141,7 +142,7 @@ export const plotConfiguration = (
   return {
     constructorOptions,
     axisConfig,
-    chartAppendConfig: [numScales, {}, catScales, margins],
+    chartAppendConfig: [numScales, {}, catScales, margins(rowDimension)],
     categoricalScales: catScales,
   };
 };
diff --git a/tests/unit/components/AppHeader.spec.ts b/tests/unit/components/AppHeader.spec.ts
new file mode 100644
index 0000000..c7881f4
--- /dev/null
+++ b/tests/unit/components/AppHeader.spec.ts
@@ -0,0 +1,26 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { setActivePinia, createPinia } from 'pinia';
+import AppHeader from '@/components/AppHeader.vue';
+
+describe('AppHeader component', () => {
+  beforeEach(() => {
+    setActivePinia(createPinia());
+  });
+
+  it('renders the about modal when the about button is clicked', async () => {
+    const wrapper = mount(AppHeader);
+    expect(wrapper.findComponent({ name: 'FwbModal' }).exists()).toBe(false);
+
+    const aboutButton = wrapper.find('button#aboutLink');
+    await aboutButton.trigger('click');
+
+    await vi.waitFor(() => {
+      expect(wrapper.findComponent({ name: 'FwbModal' }).exists()).toBe(true);
+      expect(wrapper.findComponent({ name: 'FwbModal' }).isVisible()).toBe(true);
+    })
+
+    // Check that the version number is displayed correctly
+    expect(wrapper.text()).toMatch(/Vaxviz version: \d+\.\d+\.\d+/);
+  });
+});
diff --git a/tests/unit/components/ColorLegend.spec.ts b/tests/unit/components/ColorLegend.spec.ts
index 924fb3c..0d1184d 100644
--- a/tests/unit/components/ColorLegend.spec.ts
+++ b/tests/unit/components/ColorLegend.spec.ts
@@ -7,12 +7,17 @@ import { globalOption } from '@/utils/options';
 import { useAppStore } from "@/stores/appStore";
 import { useColorStore } from '@/stores/colorStore';
 
+const expectCorrectMarginForRowDimension = (rowDimension: "disease" | "location", wrapper: ReturnType<typeof mount>) => {
+  const leftMarginPx = rowDimension === "location" ? 170 : 110;
+  expect(wrapper.find('ul').attributes('style')).toBe(`margin-left: ${leftMarginPx}px;`);
+};
+
 describe('RidgelinePlot component', () => {
   beforeEach(() => {
     setActivePinia(createPinia());
   });
 
-  it('renders the correct labels and colors when the color dimension is location, sorting them by resolution', async () => {
+  it('renders the correct labels and colours when the color dimension is location, sorting them by resolution', async () => {
     const appStore = useAppStore();
     const colorStore = useColorStore();
     const wrapper = mount(ColorLegend);
@@ -61,6 +66,8 @@ describe('RidgelinePlot component', () => {
     expect(labels[2].text()).toBe('All 117 VIMC countries');
     expect(colorBoxes[2].element.style.borderColor).toBe("rgb(105, 41, 196)"); // purple70
     expect(colorBoxes[2].element.style.backgroundColor).toBe("rgba(105, 41, 196, 0.2)");
+
+    expectCorrectMarginForRowDimension("disease", wrapper);
   });
 
   it('renders the correct labels and colors when the color dimension is disease, in the order in which the colors were assigned', async () => {
@@ -98,6 +105,8 @@ describe('RidgelinePlot component', () => {
     expect(labels[1].text()).toBe('Cholera');
     expect(colorBoxes[1].element.style.borderColor).toBe("rgb(105, 41, 196)"); // purple70
     expect(colorBoxes[1].element.style.backgroundColor).toBe("rgba(105, 41, 196, 0.2)");
+
+    expectCorrectMarginForRowDimension("disease", wrapper);
   });
 
   it('updates the legend when the data changes', async () => {
@@ -143,9 +152,8 @@ describe('RidgelinePlot component', () => {
     expect(colorBoxes[2].element.style.borderColor).toBe("rgb(105, 41, 196)"); // purple70
     expect(colorBoxes[2].element.style.backgroundColor).toBe("rgba(105, 41, 196, 0.2)");
 
-    appStore.dimensions.withinBand = 'location';
-    appStore.dimensions.column = 'activity_type';
-    appStore.dimensions.row = 'disease';
+    expectCorrectMarginForRowDimension("disease", wrapper);
+
     appStore.filters = {
       location: ['AFG'],
       disease: ['Cholera', 'Rubella'],
@@ -175,5 +183,46 @@ describe('RidgelinePlot component', () => {
     expect(diseaseLabels[1].text()).toBe('Cholera');
     expect(diseaseColorBoxes[1].element.style.borderColor).toBe("rgb(105, 41, 196)"); // purple70
     expect(diseaseColorBoxes[1].element.style.backgroundColor).toBe("rgba(105, 41, 196, 0.2)");
+    expectCorrectMarginForRowDimension("disease", wrapper);
+  });
+
+  it('renders the correct labels and colours when the _row_ dimension is location (regardless of color dimension)', async () => {
+    const appStore = useAppStore();
+    const colorStore = useColorStore();
+    const wrapper = mount(ColorLegend);
+    appStore.dimensions.withinBand = 'disease';
+    appStore.dimensions.column = null;
+    appStore.dimensions.row = 'location';
+    appStore.filters = {
+      location: ['AFG', 'global'],
+      disease: ['Malaria'],
+    };
+    expect(colorStore.colorDimension).toBe('location');
+
+    colorStore.setColors([
+      { metadata: { withinBand: 'Malaria', row: 'AFG' } },
+      { metadata: { withinBand: 'Malaria', row: 'global' } },
+    ]);
+
+    expect(colorStore.colorMapping.size).toBe(2);
+
+    await vi.waitFor(() => {
+      expect(wrapper.findAll(".legend-label").length).toBe(2);
+    });
+
+    const labels = wrapper.findAll(".legend-label");
+    const colorBoxes = wrapper.findAll(".legend-color-box");
+
+    // NB order of locations is _not_ determined by geographical resolution in this case, because the y-categorical scale
+    // is location and thus the color legend order is intended to match that.
+    expect(labels[0].text()).toBe('All 117 VIMC countries');
+    expect(colorBoxes[0].element.style.borderColor).toBe("rgb(105, 41, 196)"); // purple70
+    expect(colorBoxes[0].element.style.backgroundColor).toBe("rgba(105, 41, 196, 0.2)");
+
+    expect(labels[1].text()).toBe('Afghanistan');
+    expect(colorBoxes[1].element.style.borderColor).toBe("rgb(0, 157, 154)"); // teal50
+    expect(colorBoxes[1].element.style.backgroundColor).toBe("rgba(0, 157, 154, 0.2)");
+
+    expectCorrectMarginForRowDimension("location", wrapper);
   });
 });