diff --git a/app/components/historyView.js b/app/components/historyView.js
index 25a6306..4c232e8 100644
--- a/app/components/historyView.js
+++ b/app/components/historyView.js
@@ -30,6 +30,14 @@ const COLOR_SLOT_COUNT = 10;
  */
 export const INITIAL_VISIBLE_DAYS = 6;
 
+/**
+ * Maximum number of x-axis date labels shown on the total play-time line chart.
+ * When there are more data points than this, labels are thinned so they remain readable.
+ *
+ * @type {number}
+ */
+export const MAX_X_LABELS = 10;
+
 /**
  * Extract all unique YYYY-MM-DD date keys present across all games' dailyTime maps.
  *
@@ -163,7 +171,8 @@ export function createDataTable(summaryData, gameIds, manifests) {
  * Create a total play-time line chart showing daily totals across all games.
  *
  * Renders an SVG line chart with one data point per day connected by a line,
- * giving a quick at-a-glance trend of overall activity. Labeled with MM-DD dates.
+ * giving a quick at-a-glance trend of overall activity. X-axis is labeled with
+ * MM-DD dates, thinned to at most {@link MAX_X_LABELS} labels to avoid crowding.
  *
  * @param {Array<{date: string, total: number}>} summaryData - Per-day totals.
  * @returns {HTMLElement} A <div> element containing the total play-time line chart.
@@ -188,7 +197,7 @@ export function createTotalPlayTimeChart(summaryData) {
   const svgW = 600;
   const svgH = 120;
   const pad = {
-    top: 10, right: 20, bottom: 28, left: 10,
+    top: 10, right: 20, bottom: 28, left: 52,
   };
   const plotW = svgW - pad.left - pad.right;
   const plotH = svgH - pad.top - pad.bottom;
@@ -200,6 +209,28 @@ export function createTotalPlayTimeChart(summaryData) {
   svg.setAttribute('class', 'history-total-chart__svg');
   svg.setAttribute('role', 'img');
 
+  // Y-axis gridlines and tick labels at 0%, 50%, and 100% of scale.
+  [1, 0.5, 0].forEach((fraction) => {
+    const yPos = pad.top + plotH - Math.round(fraction * plotH);
+    const timeMs = Math.round(fraction * maxMs);
+
+    const gridLine = document.createElementNS(SVG_NS, 'line');
+    gridLine.setAttribute('x1', String(pad.left));
+    gridLine.setAttribute('y1', String(yPos));
+    gridLine.setAttribute('x2', String(svgW - pad.right));
+    gridLine.setAttribute('y2', String(yPos));
+    gridLine.setAttribute('class', 'history-total-chart__grid-line');
+    svg.appendChild(gridLine);
+
+    const yLabel = document.createElementNS(SVG_NS, 'text');
+    yLabel.setAttribute('x', String(pad.left - 4));
+    yLabel.setAttribute('y', String(yPos));
+    yLabel.setAttribute('dominant-baseline', 'middle');
+    yLabel.setAttribute('class', 'history-total-chart__y-label');
+    yLabel.textContent = formatDuration(timeMs);
+    svg.appendChild(yLabel);
+  });
+
   // Calculate pixel coordinates for each data point.
   const points = summaryData.map((d, i) => {
     const x = pad.left + (n === 1 ? plotW / 2 : (i / (n - 1)) * plotW);
@@ -216,7 +247,9 @@ export function createTotalPlayTimeChart(summaryData) {
   svg.appendChild(polyline);
 
   // Dot and date label for each point.
-  points.forEach((p) => {
+  // Thin x-axis labels so they remain readable when there are many data points.
+  const labelStep = Math.max(1, Math.ceil(n / MAX_X_LABELS));
+  points.forEach((p, i) => {
     const circle = document.createElementNS(SVG_NS, 'circle');
     circle.setAttribute('cx', p.x);
     circle.setAttribute('cy', p.y);
@@ -228,38 +261,75 @@ export function createTotalPlayTimeChart(summaryData) {
     circle.appendChild(tooltipTitle);
     svg.appendChild(circle);
 
-    const label = document.createElementNS(SVG_NS, 'text');
-    label.setAttribute('x', p.x);
-    label.setAttribute('y', svgH - 4);
-    label.setAttribute('text-anchor', 'middle');
-    label.setAttribute('class', 'history-total-chart__x-label');
-    label.textContent = p.date.slice(5); // Display as MM-DD.
-    svg.appendChild(label);
+    if (i % labelStep === 0) {
+      const label = document.createElementNS(SVG_NS, 'text');
+      label.setAttribute('x', p.x);
+      label.setAttribute('y', svgH - 4);
+      label.setAttribute('text-anchor', 'middle');
+      label.setAttribute('class', 'history-total-chart__x-label');
+      label.textContent = p.date.slice(5); // Display as MM-DD.
+      svg.appendChild(label);
+    }
   });
 
   wrapper.appendChild(svg);
   return wrapper;
 }
 
+/**
+ * Create a y-axis element for the bar chart showing time-scale labels.
+ *
+ * Renders tick labels at the top (maximum value), middle (half of maximum),
+ * and bottom (zero) of the bar area so readers can interpret bar heights.
+ *
+ * @private
+ * @param {number} maxMs - Maximum milliseconds shown at the top of the scale.
+ * @returns {HTMLElement} A div element serving as the y-axis scale indicator.
+ */
+function createBarChartYAxis(maxMs) {
+  const yAxis = document.createElement('div');
+  yAxis.className = 'history-chart__y-axis';
+
+  [maxMs, Math.round(maxMs / 2), 0].forEach((ms) => {
+    const tick = document.createElement('span');
+    tick.className = 'history-chart__y-tick';
+    tick.textContent = formatDuration(ms);
+    yAxis.appendChild(tick);
+  });
+
+  return yAxis;
+}
+
 /**
  * Build the DOM for a single day-column in the per-game bar chart.
  *
+ * Each day group scales its bars and y-axis to its own total play time, so
+ * the y-axis labels are meaningful for the specific day being displayed.
+ *
  * @param {object} dayData - Summary entry for one day.
  * @param {string[]} gameIds - Game IDs to render bars for.
- * @param {number} maxMs - Maximum total ms across all days (for scaling).
  * @param {Array<{id: string, name: string}>} [manifests] - Manifest list for names.
  * @returns {HTMLElement} A `.history-chart__group` element.
  */
-function createDayGroup(dayData, gameIds, maxMs, manifests) {
+function createDayGroup(dayData, gameIds, manifests) {
+  // Scale this group to its own total so bars fill the available height and
+  // the y-axis tick labels reflect this day's actual values.
+  const dayMaxMs = Math.max(dayData.total, 1);
+
   const group = document.createElement('div');
   group.className = 'history-chart__group';
 
+  // Body: y-axis on the left, bars on the right.
+  const groupBody = document.createElement('div');
+  groupBody.className = 'history-chart__group-body';
+  groupBody.appendChild(createBarChartYAxis(dayMaxMs));
+
   const barsWrap = document.createElement('div');
   barsWrap.className = 'history-chart__bars';
 
   gameIds.forEach((gameId, colIndex) => {
     const ms = dayData[gameId] || 0;
-    const heightPct = Math.round((ms / maxMs) * 100);
+    const heightPct = Math.round((ms / dayMaxMs) * 100);
     const bar = document.createElement('div');
     const colorIndex = colIndex % COLOR_SLOT_COUNT;
     bar.className = `history-chart__bar history-chart__bar--color-${colorIndex}`;
@@ -268,20 +338,20 @@ function createDayGroup(dayData, gameIds, maxMs, manifests) {
     barsWrap.appendChild(bar);
   });
 
-  // Total bar (grey).
-  const totalMs = dayData.total;
-  const totalPct = Math.round((totalMs / maxMs) * 100);
+  // Total bar (grey) — always 100% height since dayMaxMs === dayData.total.
   const totalBar = document.createElement('div');
   totalBar.className = 'history-chart__bar history-chart__bar--total';
-  totalBar.style.height = `${totalPct}%`;
-  totalBar.title = `Total: ${formatDuration(totalMs)}`;
+  totalBar.style.height = '100%';
+  totalBar.title = `Total: ${formatDuration(dayData.total)}`;
   barsWrap.appendChild(totalBar);
 
+  groupBody.appendChild(barsWrap);
+
   const dateLabel = document.createElement('span');
   dateLabel.className = 'history-chart__label';
   dateLabel.textContent = dayData.date.slice(5); // Display as MM-DD.
 
-  group.appendChild(barsWrap);
+  group.appendChild(groupBody);
   group.appendChild(dateLabel);
   return group;
 }
@@ -298,8 +368,6 @@ function createDayGroup(dayData, gameIds, maxMs, manifests) {
  * @returns {HTMLElement}
  */
 export function createBarChart(summaryData, gameIds, manifests) {
-  const maxMs = Math.max(...summaryData.map((d) => d.total), 1);
-
   const chartEl = document.createElement('div');
   chartEl.className = 'history-chart';
   chartEl.setAttribute('aria-hidden', 'true'); // Table is the accessible version.
@@ -316,7 +384,7 @@ export function createBarChart(summaryData, gameIds, manifests) {
   const recentGrid = document.createElement('div');
   recentGrid.className = 'history-chart__grid';
   recentData.forEach((dayData) => {
-    recentGrid.appendChild(createDayGroup(dayData, gameIds, maxMs, manifests));
+    recentGrid.appendChild(createDayGroup(dayData, gameIds, manifests));
   });
   chartEl.appendChild(recentGrid);
 
@@ -326,7 +394,7 @@ export function createBarChart(summaryData, gameIds, manifests) {
     olderGrid.className = 'history-chart__grid';
     olderGrid.hidden = true;
     olderData.forEach((dayData) => {
-      olderGrid.appendChild(createDayGroup(dayData, gameIds, maxMs, manifests));
+      olderGrid.appendChild(createDayGroup(dayData, gameIds, manifests));
     });
     chartEl.appendChild(olderGrid);
 
diff --git a/app/components/tests/historyView.test.js b/app/components/tests/historyView.test.js
index f610c39..c0e5c3d 100644
--- a/app/components/tests/historyView.test.js
+++ b/app/components/tests/historyView.test.js
@@ -19,6 +19,7 @@ import {
   createTotalPlayTimeChart,
   buildHistoryPanel,
   INITIAL_VISIBLE_DAYS,
+  MAX_X_LABELS,
 } from '../historyView.js';
 
 // ── Test fixtures ─────────────────────────────────────────────────────────────
@@ -307,9 +308,38 @@ describe('createBarChart()', () => {
     const btn = chart.querySelector('.history-chart__show-more-btn');
     expect(btn).toBeNull();
   });
-});
 
-// ── createBarChart show-more ──────────────────────────────────────────────────
+  it('includes a y-axis element', () => {
+    const chart = createBarChart(summaryData, gameIds, MANIFESTS);
+    const yAxis = chart.querySelector('.history-chart__y-axis');
+    expect(yAxis).not.toBeNull();
+  });
+
+  it('y-axis contains three tick labels per day group', () => {
+    const chart = createBarChart(summaryData, gameIds, MANIFESTS);
+    const ticks = chart.querySelectorAll('.history-chart__y-tick');
+    // 3 ticks per group × number of days in summaryData
+    expect(ticks.length).toBe(summaryData.length * 3);
+  });
+
+  it('y-axis bottom tick label shows 00:00', () => {
+    const chart = createBarChart(summaryData, gameIds, MANIFESTS);
+    const ticks = [...chart.querySelectorAll('.history-chart__y-tick')];
+    expect(ticks[ticks.length - 1].textContent).toBe('00:00');
+  });
+
+  it('each day group y-axis top tick reflects that day\'s own total time', () => {
+    // summaryData uses dates ['2024-01-01', '2024-01-02'].
+    // 2024-01-01: game-a=60000 + game-b=30000 = total 90000 ms → '01:30'
+    // 2024-01-02: game-a=120000 + game-b=0   = total 120000 ms → '02:00'
+    // Groups are rendered newest-first: [2024-01-02, 2024-01-01].
+    const chart = createBarChart(summaryData, gameIds, MANIFESTS);
+    const groups = [...chart.querySelectorAll('.history-chart__group')];
+    const topTickOf = (group) => group.querySelector('.history-chart__y-tick').textContent;
+    expect(topTickOf(groups[0])).toBe('02:00'); // 2024-01-02 total = 120000 ms
+    expect(topTickOf(groups[1])).toBe('01:30'); // 2024-01-01 total = 90000 ms
+  });
+});
 
 describe('createBarChart() show-more behaviour', () => {
   const dates = getAllDates(PROGRESS_MANY_DAYS);
@@ -429,6 +459,50 @@ describe('createTotalPlayTimeChart()', () => {
     expect(labels[0].textContent).toBe('01-01');
   });
 
+  it('shows all x-axis labels when data points are within MAX_X_LABELS', () => {
+    // summaryData has 3 points, well under MAX_X_LABELS (10)
+    const chart = createTotalPlayTimeChart(summaryData);
+    const labels = chart.querySelectorAll('.history-total-chart__x-label');
+    expect(labels.length).toBe(dates.length);
+  });
+
+  it('thins x-axis labels to at most MAX_X_LABELS when there are many data points', () => {
+    // Build summaryData with MAX_X_LABELS + 5 data points to trigger thinning.
+    const manyDates = Array.from({ length: MAX_X_LABELS + 5 }, (_, i) => {
+      const d = new Date(2024, 0, i + 1);
+      return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
+    });
+    const manyData = manyDates.map((date) => ({ date, total: 60000 }));
+    const chart = createTotalPlayTimeChart(manyData);
+    const labels = chart.querySelectorAll('.history-total-chart__x-label');
+    expect(labels.length).toBeLessThanOrEqual(MAX_X_LABELS);
+  });
+
+  it('SVG contains three y-axis labels at 0%, 50%, and 100% of scale', () => {
+    const chart = createTotalPlayTimeChart(summaryData);
+    const yLabels = chart.querySelectorAll('.history-total-chart__y-label');
+    expect(yLabels.length).toBe(3);
+  });
+
+  it('y-axis top label shows the maximum total time', () => {
+    const chart = createTotalPlayTimeChart(summaryData);
+    const yLabels = [...chart.querySelectorAll('.history-total-chart__y-label')];
+    // summaryData max total: 2024-01-02 has 120000 ms for game-a alone → "02:00"
+    expect(yLabels[0].textContent).toBe('02:00');
+  });
+
+  it('y-axis bottom label shows 00:00', () => {
+    const chart = createTotalPlayTimeChart(summaryData);
+    const yLabels = [...chart.querySelectorAll('.history-total-chart__y-label')];
+    expect(yLabels[yLabels.length - 1].textContent).toBe('00:00');
+  });
+
+  it('SVG contains three horizontal grid lines', () => {
+    const chart = createTotalPlayTimeChart(summaryData);
+    const gridLines = chart.querySelectorAll('.history-total-chart__grid-line');
+    expect(gridLines.length).toBe(3);
+  });
+
   it('includes a title paragraph', () => {
     const chart = createTotalPlayTimeChart(summaryData);
     const title = chart.querySelector('.history-total-chart__title');
diff --git a/app/styles/history.css b/app/styles/history.css
index af377d4..1fcb668 100644
--- a/app/styles/history.css
+++ b/app/styles/history.css
@@ -205,6 +205,18 @@
   fill: var(--text-subtle);
 }
 
+.history-total-chart__grid-line {
+  stroke: var(--border-color);
+  stroke-width: 1;
+  stroke-dasharray: 3 3;
+}
+
+.history-total-chart__y-label {
+  font-size: 10px;
+  fill: var(--text-subtle);
+  text-anchor: end;
+}
+
 /* ── History bar chart ───────────────────────────────────────────────────── */
 
 .history-chart {
@@ -253,7 +265,33 @@
   flex-direction: column;
   align-items: center;
   gap: 0.25rem;
-  min-width: 60px;
+}
+
+/* Flex row: per-group y-axis scale on the left, bars on the right. */
+.history-chart__group-body {
+  display: flex;
+  flex-direction: row;
+  align-items: stretch;
+}
+
+/* Per-group y-axis scale indicator (one per day cell). */
+.history-chart__y-axis {
+  display: flex;
+  flex-direction: column;
+  justify-content: space-between;
+  align-items: flex-end;
+  height: 160px; /* Must match .history-chart__bars height. */
+  padding-right: 0.25rem;
+  border-right: 1px solid var(--border-color);
+  flex-shrink: 0;
+  min-width: 1.75rem;
+}
+
+.history-chart__y-tick {
+  font-size: 0.6rem;
+  color: var(--text-subtle);
+  white-space: nowrap;
+  line-height: 1;
 }
 
 .history-chart__bar {
diff --git a/package-lock.json b/package-lock.json
index 287fef3..38d62f9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "brain-speed-exercises",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "brain-speed-exercises",
-      "version": "0.1.0",
+      "version": "0.2.0",
       "license": "MIT",
       "dependencies": {
         "electron-debug": "^4",