diff --git a/src/library.js b/src/library.js
index 514748c..e80a5a4 100644
--- a/src/library.js
+++ b/src/library.js
@@ -1,14 +1,41 @@
 'use strict'
 
 const path = require('path')
+const fs = require('fs')
 const { DIRS, readJson, writeJson } = require('./paths')
 const { prefixPath } = require('./prefixes')
 
 const REGISTRY = path.join(DIRS.DATA, 'apps.json')
 const SETTINGS = path.join(DIRS.DATA, 'settings.json')
 
+// Playtime lives in its own tiny file holding ONLY a number of seconds
+// (files/data/appdata/<id>/playtime.txt) so the running game can update it
+// every ~30s without rewriting the whole apps.json registry on each tick.
+function playtimeFile(id) {
+  return path.join(DIRS.DATA, 'appdata', id, 'playtime.txt')
+}
+
+function readPlaySeconds(id) {
+  try {
+    const n = parseInt(fs.readFileSync(playtimeFile(id), 'utf8').trim(), 10)
+    if (Number.isFinite(n) && n >= 0) return n
+  } catch {}
+  return null // no file yet -> fall back to the registry value
+}
+
+function writePlaySeconds(id, seconds) {
+  const file = playtimeFile(id)
+  fs.mkdirSync(path.dirname(file), { recursive: true })
+  fs.writeFileSync(file, String(Math.max(0, Math.round(seconds))))
+}
+
 function loadGames() {
-  return readJson(REGISTRY, [])
+  const games = readJson(REGISTRY, [])
+  for (const g of games) {
+    const ps = readPlaySeconds(g.id)
+    if (ps != null) g.playSeconds = ps
+  }
+  return games
 }
 
 function saveGames(games) {
@@ -30,11 +57,18 @@ function updateGame(id, patch) {
   const games = loadGames()
   const g = games.find(x => x.id === id)
   if (!g) return null
+  // playSeconds goes to its own tiny file; the registry just mirrors it for
+  // anything reading apps.json directly (loadGames prefers the file anyway).
+  if (patch.playSeconds !== undefined) writePlaySeconds(id, patch.playSeconds)
   Object.assign(g, patch)
   saveGames(games)
   return g
 }
 
+function clearPlaytime(id) {
+  return updateGame(id, { playSeconds: 0, lastPlayed: 0 })
+}
+
 function removeGame(id) {
   const games = loadGames()
   const idx = games.findIndex(g => g.id === id)
@@ -86,4 +120,4 @@ function resolvePrefixDir(game) {
   return prefixPath(defs.default || 'default')
 }
 
-module.exports = { loadGames, saveGames, getGame, addGame, updateGame, removeGame, loadSettings, saveSettings, newGame, resolvePrefixDir }
+module.exports = { loadGames, saveGames, getGame, addGame, updateGame, removeGame, loadSettings, saveSettings, newGame, resolvePrefixDir, clearPlaytime, readPlaySeconds, writePlaySeconds, playtimeFile }
diff --git a/src/main.js b/src/main.js
index 1414e49..b86f69e 100644
--- a/src/main.js
+++ b/src/main.js
@@ -110,7 +110,7 @@ ipcMain.handle('games:list', () => library.loadGames())
 ipcMain.handle('games:remove', (e, id) => library.removeGame(id))
 ipcMain.handle('games:get', (e, id) => library.getGame(id))
 ipcMain.handle('games:update', (e, id, patch) => library.updateGame(id, patch))
-ipcMain.handle('games:clearPlaytime', (e, id) => library.updateGame(id, { playSeconds: 0, lastPlayed: 0 }))
+ipcMain.handle('games:clearPlaytime', (e, id) => library.clearPlaytime(id))
 ipcMain.handle('games:resetIcon', (e, id) => {
   const game = library.getGame(id)
   if (!game) return { ok: false }
diff --git a/src/runner.js b/src/runner.js
index b0070ca..651fdcb 100644
--- a/src/runner.js
+++ b/src/runner.js
@@ -77,15 +77,16 @@ function parseArgs(args) {
 
 const GRACE_MS = 60000
 
-// Live playtime: update stats while the game is still running (not only on exit).
-function startPlaytimeTicker({ game, startedAt, onTick }) {
+// Live playtime: while the game runs, update ONLY the tiny playtime file
+// (a number of seconds) every 30s - apps.json is left untouched to spare the
+// disk. lastPlayed is stamped once at start, final totals are mirrored into
+// the registry once on exit.
+function startPlaytimeTicker({ game, startedAt }) {
+  const library = require('./library')
+  const base = game.playSeconds || 0
   const timer = setInterval(() => {
     const counted = Math.max(0, Math.round((Date.now() - startedAt - GRACE_MS) / 1000))
-    require('./library').updateGame(game.id, {
-      lastPlayed: startedAt,
-      playSeconds: (game.playSeconds || 0) + counted
-    })
-    if (onTick) onTick()
+    library.writePlaySeconds(game.id, base + counted)
   }, 30000)
   return () => clearInterval(timer)
 }
@@ -147,6 +148,8 @@ function runGame({ game, wine, systemWine, onExit }) {
     child.unref()
     const startedAt = Date.now()
     const stopTicker = startPlaytimeTicker({ game, startedAt })
+    // stamp "last played" once at start so it is correct even if we crash later
+    require('./library').updateGame(game.id, { lastPlayed: startedAt })
     child.on('exit', (code, signal) => {
       stopTicker()
       ws.end()