diff --git a/NotoSansMath-subset.woff2 b/NotoSansMath-subset.woff2
new file mode 100644
index 0000000..7cddac9
Binary files /dev/null and b/NotoSansMath-subset.woff2 differ
diff --git a/NotoSansSymbols2-subset.woff2 b/NotoSansSymbols2-subset.woff2
new file mode 100644
index 0000000..bd64a68
Binary files /dev/null and b/NotoSansSymbols2-subset.woff2 differ
diff --git a/app.js b/app.js
index 75871ac..4054b59 100644
--- a/app.js
+++ b/app.js
@@ -34,6 +34,7 @@ const STRINGS = {
     congratulations: 'Congratulations!',
     pleaseSelect: 'Please select all options',
     installApp: 'Install App',
+    theoryUnavailable: 'Content unavailable',
     sec: 'sec',
     chooseAnswer: 'Choose answer',
     enterEquivalent: 'Enter equivalent',
@@ -75,6 +76,7 @@ const STRINGS = {
     congratulations: '\u041F\u043E\u0437\u0434\u0440\u0430\u0432\u043B\u044F\u0435\u043C!',
     pleaseSelect: '\u041F\u043E\u0436\u0430\u043B\u0443\u0439\u0441\u0442\u0430, \u0432\u044B\u0431\u0435\u0440\u0438\u0442\u0435 \u0432\u0441\u0435 \u043F\u0430\u0440\u0430\u043C\u0435\u0442\u0440\u044B',
     installApp: '\u0423\u0441\u0442\u0430\u043D\u043E\u0432\u0438\u0442\u044C \u043F\u0440\u0438\u043B\u043E\u0436\u0435\u043D\u0438\u0435',
+    theoryUnavailable: '\u041C\u0430\u0442\u0435\u0440\u0438\u0430\u043B \u043D\u0435\u0434\u043E\u0441\u0442\u0443\u043F\u0435\u043D',
     sec: '\u0441\u0435\u043A',
     chooseAnswer: '\u0412\u044B\u0431\u0435\u0440\u0438\u0442\u0435 \u043E\u0442\u0432\u0435\u0442',
     enterEquivalent: '\u0412\u0432\u0435\u0434\u0438\u0442\u0435 \u0447\u0438\u0441\u043B\u043E',
@@ -113,6 +115,55 @@ function applyTranslations() {
   });
 }
 
+function refreshDynamicText() {
+  const active = document.querySelector('.screen.active');
+  if (!active) return;
+  switch (active.id) {
+    case 'screen-setup-system':
+      renderSetupSystem();
+      break;
+    case 'screen-setup-range':
+      renderSetupRange();
+      break;
+    case 'screen-setup-options':
+      document.querySelectorAll('#setup-modes .option-btn').forEach((btn, i) => {
+        btn.textContent = t(MODES[i].labelKey);
+      });
+      [...document.getElementById('setup-timing').options].forEach((opt, i) => {
+        opt.textContent = TIMINGS[i].value === 0 ? t('noLimit') : TIMINGS[i].value + ' ' + t('sec');
+      });
+      break;
+    case 'screen-theory-system':
+      renderTheorySystem();
+      break;
+    case 'screen-theory-content':
+      document.getElementById('theory-title').textContent = systemName(lastTheoryKey);
+      break;
+    case 'screen-game':
+      if (game.system && game.range) {
+        document.getElementById('score-system-range').textContent = systemName(game.system) + ': ' + game.range.label;
+      }
+      break;
+    case 'screen-results': {
+      const completed = game.currentRound >= game.rounds;
+      const total = completed ? game.rounds : game.currentRound;
+      const pct = total > 0 ? Math.round((game.correctCount / total) * 100) : 0;
+      document.getElementById('results-summary').innerHTML =
+        '<div class="big-number">' + game.correctCount + '/' + total + '</div>' +
+        '<div>' + t('pctCorrect', {pct: pct}) + '</div>';
+      const labelEl = document.getElementById('results-mistakes-label');
+      if (game.mistakes.length > 0 || labelEl.style.display !== 'none') {
+        labelEl.textContent = t('mistakes');
+      }
+      const congratsEl = document.getElementById('results-congrats');
+      if (congratsEl.textContent) {
+        congratsEl.textContent = t('congratulations');
+      }
+      break;
+    }
+  }
+}
+
 const SYSTEM_RANGES = {
   binary: [
     { label: '2\u2070 \u2013 2\u00B3', min: 1, max: 8 },
@@ -188,6 +239,7 @@ const SYSTEM_GROUPS = {
 };
 
 const theoryCache = {};
+let lastTheoryKey = null;
 
 const MODES = [
   { labelKey: 'choose', value: 'choice' },
@@ -222,11 +274,19 @@ let game = {
 };
 
 let popstateHandled = false;
+let navDepth = 0;
 
 function showScreen(id) {
   document.querySelectorAll('.screen').forEach(s => s.classList.remove('active'));
   document.getElementById('screen-' + id).classList.add('active');
-  if (id !== 'menu' && !popstateHandled) {
+  if (id === 'menu') {
+    if (navDepth > 0) {
+      const n = navDepth;
+      navDepth = 0;
+      history.go(-n);
+    }
+  } else if (!popstateHandled) {
+    navDepth++;
     history.pushState({ screen: id }, '');
   }
   popstateHandled = false;
@@ -354,7 +414,7 @@ const MARK_INCORRECT = '\u2717 ';
 function startGame() {
   lastSetupState = { ...setupState };
   game.system = setupState.system;
-  game.range = setupState.rangeData || RANGES[setupState.range];
+  game.range = setupState.rangeData;
   game.mode = MODES[setupState.mode]?.value ?? setupState.mode;
   game.timing = TIMINGS[setupState.timing]?.value ?? setupState.timing;
   game.rounds = ROUNDS[setupState.rounds];
@@ -754,12 +814,11 @@ function renderTheorySystem() {
 }
 
 async function showTheoryContent(key) {
+  lastTheoryKey = key;
   const html = await loadTheory(key);
-  if (!html) return;
-
   document.getElementById('theory-title').textContent = systemName(key);
-  document.getElementById('theory-scroll').innerHTML = html;
-
+  document.getElementById('theory-scroll').innerHTML =
+    html || '<div class="theory-unavailable">' + t('theoryUnavailable') + '</div>';
   showScreen('theory-content');
 }
 
@@ -790,9 +849,6 @@ function getPreferredTheme() {
   return window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
 }
 
-const isLightTheme = getPreferredTheme() === 'light';
-const TICKER_COLORS = isLightTheme ? TICKER_COLORS_LIGHT : TICKER_COLORS_DARK;
-
 const TICKER_SYSTEMS = [
   { key: 'binary',    min: 1,   max: 255,  suffix: toSubscript(2) },
   { key: 'base3',     min: 1,   max: 81,   suffix: toSubscript(3) },
@@ -806,6 +862,9 @@ const TICKER_SYSTEMS = [
 ];
 
 function generateTickerText() {
+  const palette = document.documentElement.dataset.theme === 'light'
+    ? TICKER_COLORS_LIGHT
+    : TICKER_COLORS_DARK;
   const pairs = [];
   let lastKey = null;
   let lastColor = null;
@@ -818,7 +877,7 @@ function generateTickerText() {
 
     let color;
     do {
-      color = TICKER_COLORS[Math.floor(Math.random() * TICKER_COLORS.length)];
+      color = palette[Math.floor(Math.random() * palette.length)];
     } while (color === lastColor);
     lastColor = color;
     const num = sys.min + Math.floor(Math.random() * (sys.max - sys.min + 1));
@@ -834,8 +893,10 @@ function generateTickerText() {
   return pairs.join('\u00A0\u00A0\u00A0\u00A0\u00A0\u00A0');
 }
 
-const tickerText = generateTickerText();
-document.getElementById('ticker').innerHTML = tickerText + '\u00A0\u00A0\u00A0\u00A0\u00A0\u00A0' + tickerText;
+function refreshTicker() {
+  const tickerText = generateTickerText();
+  document.getElementById('ticker').innerHTML = tickerText + '\u00A0\u00A0\u00A0\u00A0\u00A0\u00A0' + tickerText;
+}
 
 const langSelect = document.getElementById('lang-select');
 langSelect.value = LANG;
@@ -843,6 +904,7 @@ langSelect.addEventListener('change', () => {
   LANG = langSelect.value;
   localStorage.setItem('numnum-lang', LANG);
   applyTranslations();
+  refreshDynamicText();
 });
 
 applyTranslations();
@@ -850,6 +912,7 @@ applyTranslations();
 function applyTheme(theme) {
   document.documentElement.dataset.theme = theme;
   document.getElementById('theme-toggle').textContent = theme === 'dark' ? '\u2600' : '\u263E';
+  refreshTicker();
 }
 
 applyTheme(getPreferredTheme());
@@ -918,7 +981,8 @@ document.getElementById('btn-options-back').addEventListener('click', () => {
 });
 
 document.getElementById('btn-play').addEventListener('click', () => {
-  if (setupState.mode === undefined || setupState.timing === undefined || setupState.rounds === undefined) {
+  if (!setupState.system || !setupState.rangeData ||
+      setupState.mode === undefined || setupState.timing === undefined || setupState.rounds === undefined) {
     showSetupMessage(t('pleaseSelect'));
     return;
   }
@@ -997,6 +1061,7 @@ const BACK_MAP = {
 };
 
 window.addEventListener('popstate', () => {
+  navDepth = Math.max(0, navDepth - 1);
   const active = document.querySelector('.screen.active');
   if (!active) return;
 
diff --git a/index.html b/index.html
index 777268a..09b3caa 100644
--- a/index.html
+++ b/index.html
@@ -10,7 +10,7 @@
   <link rel="manifest" href="manifest.json">
   <link rel="icon" type="image/svg+xml" href="icon.svg">
   <link rel="apple-touch-icon" href="icon-192.png">
-  <link rel="stylesheet" href="styles.css?v=26">
+  <link rel="stylesheet" href="styles.css">
 </head>
 <body>
   <div id="app">
@@ -193,10 +193,10 @@
 
   </div>
 
-  <script type="module" src="app.js?v=26"></script>
+  <script type="module" src="app.js"></script>
   <script>
     if ('serviceWorker' in navigator) {
-      navigator.serviceWorker.register('/sw.js?v=26').catch(() => {});
+      navigator.serviceWorker.register('/sw.js').catch(() => {});
     }
   </script>
 </body>
diff --git a/styles.css b/styles.css
index b052d94..fb72c31 100644
--- a/styles.css
+++ b/styles.css
@@ -73,13 +73,31 @@ html[data-theme="light"] {
   font-display: swap;
 }
 
+@font-face {
+  font-family: 'Noto Sans Symbols 2';
+  src: url('NotoSansSymbols2-subset.woff2') format('woff2');
+  font-weight: normal;
+  font-style: normal;
+  font-display: swap;
+  unicode-range: U+232B, U+23F1, U+2600, U+2713, U+2717, U+2801, U+2803, U+2809-280B, U+2811, U+2813, U+2819-281B, U+283C, U+2B95;
+}
+
+@font-face {
+  font-family: 'Noto Sans Symbols 2';
+  src: url('NotoSansMath-subset.woff2') format('woff2');
+  font-weight: normal;
+  font-style: normal;
+  font-display: swap;
+  unicode-range: U+2295-2296, U+263E;
+}
+
 html, body {
   height: 100%;
   overflow: hidden;
 }
 
 body {
-  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans Symbols 2', sans-serif;
   background: var(--bg);
   color: var(--text);
   -webkit-tap-highlight-color: transparent;
@@ -189,7 +207,7 @@ body {
   white-space: nowrap;
   color: var(--text-dim);
   font-size: 1.3rem;
-  font-family: monospace;
+  font-family: 'Noto Sans Symbols 2', monospace;
   animation: ticker-scroll 40s linear infinite;
 }
 
@@ -455,7 +473,7 @@ body {
 }
 
 .number-display.mono {
-  font-family: monospace;
+  font-family: 'Noto Sans Symbols 2', monospace;
 }
 
 .ticker .slavonic-font {
@@ -795,13 +813,19 @@ body {
   background: var(--bg-card);
   border-radius: 8px;
   padding: 16px;
-  font-family: monospace;
+  font-family: 'Noto Sans Symbols 2', monospace;
   font-size: 1.1rem;
   margin: 12px 0;
   text-align: center;
   letter-spacing: 2px;
 }
 
+.theory-unavailable {
+  text-align: center;
+  opacity: 0.65;
+  padding: 24px 0;
+}
+
 .theory-scroll .slavonic-font {
   font-family: 'Ponomar', serif;
   font-size: 1.4rem;
diff --git a/sw.js b/sw.js
index fd6c2b8..016558a 100644
--- a/sw.js
+++ b/sw.js
@@ -1,4 +1,4 @@
-const CACHE_NAME = 'numnum-v27';
+const CACHE_NAME = 'numnum-v28';
 const ASSETS = [
   '/',
   '/index.html',
@@ -9,6 +9,9 @@ const ASSETS = [
   '/icon.svg',
   '/icon-192.png',
   '/icon-512.png',
+  '/Ponomar-Regular.woff',
+  '/NotoSansSymbols2-subset.woff2',
+  '/NotoSansMath-subset.woff2',
   '/theory/base3.en.html',
   '/theory/base3.ru.html',
   '/theory/binary.en.html',
@@ -33,7 +36,15 @@ const ASSETS = [
 
 self.addEventListener('install', (e) => {
   e.waitUntil(
-    caches.open(CACHE_NAME).then(cache => cache.addAll(ASSETS))
+    caches.open(CACHE_NAME).then(cache =>
+      Promise.allSettled(ASSETS.map(url => cache.add(url)))
+    ).then(results => {
+      results.forEach((r, i) => {
+        if (r.status === 'rejected') {
+          console.warn('SW precache failed:', ASSETS[i], r.reason);
+        }
+      });
+    })
   );
   self.skipWaiting();
 });