/* ===== EASY CHINESE · Full Stylesheet ===== */
@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+SC:wght@400;500;600;700;900&family=ZCOOL+QingKe+HuangYou&family=Ma+Shan+Zheng&family=Inter:wght@300;400;500;600&display=swap');

:root {
  --bg:#F5F0E1; --surface:#FFFFF0; --surface2:#EDE6D6; --surface3:#DDD4C0;
  --primary:#C23B22; --primary-dark:#9A2E1A; --primary-light:#D4604A;
  --secondary:#4A6C8F; --secondary-light:#E8EDF3;
  --accent:#C89B3C; --success:#3E6B48; --warning:#D4A017;
  --text:#2C2C2C; --text2:#5A5A4A; --text3:#8A8A7A;
  --radius:8px; --radius-lg:16px;
  --shadow:0 2px 8px rgba(44,44,44,.08);
  --shadow-lg:0 6px 24px rgba(44,44,44,.1);
  --transition:.3s cubic-bezier(.4,0,.2,1);
  --font-title:'ZCOOL QingKe HuangYou','Noto Serif SC',serif;
  --font-body:'Noto Serif SC','Ma Shan Zheng',serif;
}
/* Performance: contain paint for sidebar, reduce re-paint regions */
.sidebar{contain:strict;will-change:transform}
.main{contain:layout;min-height:100vh}
.page{content-visibility:auto;contain-intrinsic-size:1200px}
.page.active{content-visibility:visible}
/* Smooth theme transitions */
body,.card,.page,.profile-banner,.toast,.modal,.modal-content,.sidebar{
  transition:background-color .35s ease,color .3s ease,border-color .3s ease;
}
[data-theme="dark"] {
  --bg:#1a1a2e; --surface:#16213e; --surface2:#1a2744; --surface3:#243356;
  --primary:#e85d3a; --primary-dark:#c94a2a; --primary-light:#f0806a;
  --secondary:#7eb8da; --secondary-light:#1e3048;
  --accent:#d4a83c; --success:#5c9a6b; --warning:#e0b820;
  --text:#e8e0d0; --text2:#b0a898; --text3:#787060;
  --shadow:0 2px 8px rgba(0,0,0,.3);
  --shadow-lg:0 6px 24px rgba(0,0,0,.4);
}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:'Noto Serif SC','Ma Shan Zheng',serif;
  background:var(--bg);color:var(--text);line-height:1.7;
  display:flex;min-height:100vh;
  background-image:
    repeating-linear-gradient(0deg, transparent, transparent 3px, rgba(139,119,90,.03) 3px, rgba(139,119,90,.03) 4px),
    repeating-linear-gradient(90deg, transparent, transparent 3px, rgba(139,119,90,.03) 3px, rgba(139,119,90,.03) 4px);
}
a{color:var(--secondary);text-decoration:none}
a:hover{text-decoration:underline}

/* ===== SIDEBAR ===== */
.sidebar{
  width:260px;flex-shrink:0;background:var(--surface);
  border-right:2px solid var(--surface3);
  display:flex;flex-direction:column;position:sticky;top:0;height:100vh;overflow-y:auto;
  z-index:100;transition:transform .3s;
}
.sidebar::before{
  content:'';position:absolute;top:0;left:0;right:0;height:4px;
  background:linear-gradient(90deg,var(--primary),var(--accent));
}
.sidebar-logo{
  padding:20px 20px 12px;display:flex;align-items:center;gap:12px;
  border-bottom:1px solid var(--surface3);
}
.sidebar-logo .icon{
  width:40px;height:40px;border-radius:50%;
  object-fit:cover;flex-shrink:0;border:2px solid var(--accent);
}
.sidebar-logo h1{font-size:18px;font-weight:700;line-height:1.2;font-family:var(--font-title)}
.sidebar-logo h1 small{display:block;font-size:11px;font-weight:400;color:var(--text3);letter-spacing:2px;font-family:var(--font-body)}
.sidebar-nav{padding:12px 10px;flex:1}
.nav-item{
  display:flex;align-items:center;gap:10px;
  padding:10px 14px;border-radius:6px;cursor:pointer;
  font-size:14px;font-weight:500;color:var(--text2);
  transition:all .2s;border:none;background:none;width:100%;text-align:left;font-family:var(--font-body);
  border-left:2px solid transparent;
}
.nav-item:hover{background:var(--surface2);color:var(--text);border-left-color:var(--accent)}
.nav-item.active{
  background:linear-gradient(135deg,rgba(194,59,34,.06),rgba(200,155,60,.06));
  color:var(--primary);font-weight:700;
  border-left-color:var(--primary);
  font-family:var(--font-title);
}
.nav-item .nav-icon{font-size:16px;width:22px;text-align:center}
.nav-item .nav-badge{
  margin-left:auto;background:var(--primary);color:var(--surface);
  font-size:10px;padding:1px 7px;border-radius:10px;font-weight:600;
}
.theme-toggle{width:36px;height:36px;border-radius:50%;border:1px solid var(--surface3);background:var(--surface2);cursor:pointer;font-size:16px;display:flex;align-items:center;justify-content:center;margin:0 auto 8px;transition:var(--transition)}.theme-toggle:hover{background:var(--surface3);transform:scale(1.1)}
.sp-btn{cursor:pointer;font-size:12px;margin-left:3px;opacity:.7;transition:opacity .2s}.sp-btn:hover{opacity:1}
.fc-spk{position:absolute;top:8px;right:8px;font-size:18px;cursor:pointer;opacity:.6;transition:opacity .2s;z-index:2}.fc-spk:hover{opacity:1}
/* Settings theme toggle slider */
#profileThemeToggle:checked ~ .theme-slider-bg{background:linear-gradient(135deg,var(--secondary),var(--accent))!important;border-color:var(--accent)!important}
#profileThemeToggle:checked ~ .theme-slider-knob{transform:translateX(22px);background:var(--accent)!important}
.sidebar-footer{
  padding:14px 20px;border-top:1px solid var(--surface3);
  font-size:11px;color:var(--text3);text-align:center;
  font-family:var(--font-body);
}
.beian-info{margin-top:6px}
.beian-info a{color:var(--text3);text-decoration:none;font-size:10px;display:block;line-height:1.6}
.beian-info a:hover{color:var(--text2)}
.goog-te-banner-frame{display:none!important}
body{top:0!important}

/* Definition dropdown */
.definition-toggle{
  max-width:200px;
  overflow:hidden;
  text-overflow:ellipsis;
  white-space:nowrap;
  cursor:pointer;
  position:relative;
  padding-right:16px !important;
}
.definition-toggle::after{
  content:'▼';
  position:absolute;
  right:4px;
  top:50%;
  transform:translateY(-50%);
  font-size:8px;
  color:var(--text3);
}
.definition-toggle.definition-expanded{
  white-space:normal;
  overflow:visible;
  max-width:none;
}
.definition-toggle.definition-expanded::after{
  content:'▲';
}

/* ===== 古风印章装饰 ===== */
.seal-stamp{
  display:inline-flex;align-items:center;justify-content:center;
  width:36px;height:36px;border:2px solid var(--primary);
  border-radius:4px;transform:rotate(-6deg);
  font-family:'Ma Shan Zheng',cursive;font-size:14px;
  color:var(--primary);background:rgba(194,59,34,.04);
  box-shadow:2px 2px 0 rgba(194,59,34,.15);
  line-height:1;flex-shrink:0;
}
.seal-stamp-sm{width:28px;height:28px;font-size:10px;border-width:1.5px;}

/* ===== 装饰分隔线 ===== */
.divider-ornament{
  text-align:center;padding:12px 0;color:var(--accent);
  font-size:14px;letter-spacing:6px;opacity:.4;
  font-family:var(--font-title);
}
.divider-ornament::before{content:'◆ ◇ ◆ ◇ ◆'}

/* ===== 描金效果 ===== */
.gold-text{
  background:linear-gradient(135deg,#d4af37 0%,#f9e6a3 30%,#d4af37 50%,#b8860b 70%,#d4af37 100%);
  background-size:300% 300%;
  -webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;
  animation:goldShimmer 4s ease infinite alternate;
}
@keyframes goldShimmer{0%{background-position:0% 50%}100%{background-position:100% 50%}}
.gold-border{border:1px solid transparent;border-image:linear-gradient(135deg,#d4af37,#f9e6a3,#b8860b,#d4af37);border-image-slice:1}
.gold-bottom{border-bottom:2px solid transparent;border-image:linear-gradient(90deg,#d4af37,#f9e6a3,#b8860b);border-image-slice:1}

/* ===== 滚动入场动画 ===== */
.scroll-in{
  opacity:0;transform:translateY(40px);
  transition:opacity .8s ease,transform .8s ease;
}
.scroll-in.visible{opacity:1;transform:translateY(0)}
.scroll-in-left{opacity:0;transform:translateX(-40px);transition:opacity .8s ease,transform .8s ease}
.scroll-in-left.visible{opacity:1;transform:translateX(0)}
.scroll-in-right{opacity:0;transform:translateX(40px);transition:opacity .8s ease,transform .8s ease}
.scroll-in-right.visible{opacity:1;transform:translateX(0)}

/* ===== 高级卡片 ===== */
.card-premium{
  position:relative;background:var(--surface);border-radius:var(--radius-lg);
  padding:28px;box-shadow:var(--shadow);
  border:1px solid var(--surface3);transition:all .4s;
  overflow:hidden;
}
.card-premium::before{
  content:'';position:absolute;top:0;left:0;right:0;height:3px;
  background:linear-gradient(90deg,var(--primary),var(--accent),var(--secondary));
  opacity:0;transition:opacity .4s;
}
.card-premium:hover{box-shadow:var(--shadow-lg);transform:translateY(-3px)}
.card-premium:hover::before{opacity:1}

/* ===== 墨韵装饰 ===== */
.ink-accent{
  position:relative;overflow:hidden;
}
.ink-accent::after{
  content:'';position:absolute;bottom:-20px;right:-20px;
  width:120px;height:120px;
  background:radial-gradient(circle,rgba(44,44,44,.03) 0%,transparent 70%);
  border-radius:50%;pointer-events:none;
}

/* ===== 花格装饰角 ===== */
.corner-deco{
  position:absolute;width:24px;height:24px;
  border-color:var(--accent);border-style:solid;
  pointer-events:none;opacity:.5;
}
.corner-tl{top:8px;left:8px;border-width:2px 0 0 2px;border-radius:4px 0 0 0}
.corner-tr{top:8px;right:8px;border-width:2px 2px 0 0;border-radius:0 4px 0 0}
.corner-bl{bottom:8px;left:8px;border-width:0 0 2px 2px;border-radius:0 0 0 4px}
.corner-br{bottom:8px;right:8px;border-width:0 2px 2px 0;border-radius:0 0 4px 0}
.main{flex:1;min-width:0;padding:0}
.page{display:none;padding:32px 40px 60px;max-width:1100px}
.page.active{display:block}
.page-in{animation:fadeUp .4s cubic-bezier(.4,0,.2,1)}
@keyframes fadeUp{from{opacity:0;transform:translateY(12px) scale(.98)}to{opacity:1;transform:translateY(0) scale(1)}}

.page-header{margin-bottom:24px;position:relative}
.page-header::after{
  content:'';display:block;width:60px;height:3px;margin-top:8px;
  background:linear-gradient(90deg,var(--accent),var(--primary));
  border-radius:2px;
}
.page-header h2{font-size:28px;font-weight:800;letter-spacing:-.5px;font-family:var(--font-title);color:var(--text)}
.page-header p{color:var(--text3);font-size:15px;margin-top:4px}

/* ===== CARDS ===== */
.card{
  background:var(--surface);border-radius:var(--radius-lg);
  padding:28px;box-shadow:var(--shadow);
  border:1px solid var(--surface3);transition:box-shadow .3s;
}
.card-hover:hover{box-shadow:var(--shadow-lg);transform:translateY(-2px)}
.card-header{font-size:15px;font-weight:600;margin-bottom:16px;display:flex;align-items:center;gap:8px;font-family:var(--font-title);color:var(--primary)}

/* ===== GRID ===== */
.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:16px}
.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}
.grid-4{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.grid-6{display:grid;grid-template-columns:repeat(6,1fr);gap:8px}
@media(max-width:900px){.grid-2,.grid-3,.grid-4,.grid-6{grid-template-columns:1fr 1fr}}
@media(max-width:600px){.grid-2,.grid-3,.grid-4,.grid-6{grid-template-columns:1fr}}

/* ===== BUTTONS ===== */
.btn{
  display:inline-flex;align-items:center;gap:8px;
  padding:10px 22px;border-radius:6px;border:none;
  font-family:var(--font-body);font-size:14px;font-weight:500;cursor:pointer;
  transition:all .2s;text-decoration:none;
  -webkit-tap-highlight-color:transparent;
}
.btn:active{transform:scale(.97)}
.btn-primary{
  background:var(--primary);color:var(--surface);
  box-shadow:0 2px 8px rgba(194,59,34,.3);
  font-family:var(--font-title);
}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 4px 16px rgba(194,59,34,.4)}
.btn-secondary{background:var(--surface2);color:var(--text);border:1px solid var(--surface3)}
.btn-secondary:hover{background:var(--surface3)}
.btn-outline{background:transparent;color:var(--primary);border:2px solid var(--primary)}
.btn-outline:hover{background:rgba(194,59,34,.06)}
.btn-sm{padding:6px 14px;font-size:12px}
.btn-block{width:100%;justify-content:center}
.btn-ghost{background:transparent;color:var(--text2);border:none}
.btn-ghost:hover{background:var(--surface2)}

/* ===== HERO ===== */
.hero{
  text-align:center;padding:48px 20px 36px;
  background:linear-gradient(135deg,#FDF6EE 0%,#F5F0E1 50%,#F0EDE8 100%);
  border-radius:var(--radius-lg);margin-bottom:28px;
  position:relative;overflow:hidden;
  border:1px solid var(--surface3);
}
.hero::before{
  content:'学';position:absolute;top:-30px;right:-10px;
  font-size:200px;font-weight:900;color:rgba(194,59,34,.04);
  line-height:1;pointer-events:none;
  font-family:var(--font-title);
}
.hero h1{font-size:36px;font-weight:900;letter-spacing:2px;margin-bottom:8px;font-family:var(--font-title)}
.hero h1 span{background:linear-gradient(135deg,#d4af37 0%,#f9e6a3 30%,#d4af37 50%,#b8860b 70%,#d4af37 100%);background-size:300% 300%;-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;animation:goldShimmer 4s ease infinite alternate}
.hero p{font-size:15px;color:var(--text2);max-width:520px;margin:0 auto 24px}
.hero-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}
.hero-stats{display:flex;gap:40px;justify-content:center;margin-top:28px;flex-wrap:wrap}
.hero-stats div{text-align:center}
.hero-stats .num{font-size:28px;font-weight:800;color:var(--primary)}
.hero-stats .lbl{font-size:13px;color:var(--text3);overflow-wrap:break-word}

/* Level selector */
.level-selector{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;margin-bottom:28px}
.level-btn{
  padding:14px 24px;border-radius:12px;background:var(--surface);
  border:1px solid rgba(0,0,0,.06);cursor:pointer;transition:all .25s;
  text-align:center;min-width:140px;font-family:inherit;
}
.level-btn:hover{transform:translateY(-2px);box-shadow:var(--shadow);border-color:var(--primary)}
.level-btn .level-title{font-size:15px;font-weight:600;color:var(--text);overflow-wrap:break-word}
.level-btn .level-desc{font-size:12px;color:var(--text3);margin-top:2px}

/* Feature grid */
.feature-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-bottom:28px}
@media(max-width:800px){.feature-grid{grid-template-columns:1fr 1fr}}
@media(max-width:500px){.feature-grid{grid-template-columns:1fr}}
.feature-card{
  padding:24px;border-radius:var(--radius-lg);background:var(--surface);
  border:1px solid rgba(0,0,0,.04);transition:all .3s;cursor:pointer;
  overflow-wrap:break-word;word-break:break-word;
}
.feature-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}
.feature-card .fc-icon{font-size:32px;margin-bottom:10px}
.feature-card h3{font-size:16px;font-weight:600;margin-bottom:4px}
.feature-card p{font-size:13px;color:var(--text3);line-height:1.4}

/* Path visualization */
.path-viz{display:flex;align-items:center;justify-content:center;gap:0;flex-wrap:wrap;padding:20px 0}
.path-step{display:flex;flex-direction:column;align-items:center;gap:4px;padding:10px 18px;position:relative}
.path-step .circle{
  width:36px;height:36px;border-radius:50%;display:flex;align-items:center;justify-content:center;
  font-size:16px;font-weight:700;color:#fff;background:var(--surface3);color:var(--text3);
}
.path-step.completed .circle{background:var(--success);color:#fff}
.path-step.current .circle{background:linear-gradient(135deg,var(--primary),var(--accent));box-shadow:0 4px 16px rgba(233,78,78,.3)}
.path-step .plbl{font-size:12px;color:var(--text3);font-weight:500}
.path-arrow{font-size:14px;color:var(--text3);padding:0 4px}

/* ===== PINYIN ===== */
.pinyin-section{margin-bottom:24px}
.pinyin-section h3{font-size:16px;font-weight:600;margin-bottom:10px;color:var(--text2)}
.pinyin-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(80px,1fr));gap:6px}
.pinyin-cell{
  padding:12px 8px;border-radius:10px;background:var(--surface);
  border:1px solid var(--surface3);text-align:center;font-size:18px;font-weight:600;
  transition:all .2s;cursor:pointer;
}
.pinyin-cell:hover{background:var(--primary);color:#fff;border-color:var(--primary);transform:scale(1.05)}
.pinyin-cell .py-tone{font-size:11px;color:var(--text3);display:block}
.pinyin-cell:hover .py-tone{color:rgba(255,255,255,.7)}
.pinyin-cell .spk-btn{font-size:11px;margin-left:2px;opacity:.5;vertical-align:middle}
.pinyin-cell:hover .spk-btn{opacity:1}

/* ===== CHARACTERS ===== */
.char-display{text-align:center;padding:20px}
.char-display .big-char{font-size:90px;font-weight:300;line-height:1.2}
.char-strokes{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-top:12px}
.char-stroke-box{
  width:44px;height:44px;border-radius:8px;background:var(--surface2);
  display:flex;align-items:center;justify-content:center;
  font-size:24px;transition:all .2s;cursor:pointer;
}
.char-stroke-box.active{border:2px solid var(--primary);background:rgba(233,78,78,.06)}
/* Writing practice canvas */
.write-canvas-wrap{
  position:relative;display:inline-block;
  border:2px solid var(--border);border-radius:12px;
  overflow:hidden;background:#faf6ed;
}
.write-canvas-wrap canvas{
  display:block;touch-action:none;
}
.write-trace-char{
  position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);
  font-size:180px;color:rgba(0,0,0,.08);pointer-events:none;
  font-family:'KaiTi','STKaiti','楷体',serif;
  white-space:nowrap;user-select:none;
}

/* ===== QUIZ ===== */
.quiz-card{max-width:600px;margin:0 auto}
.quiz-progress{display:flex;gap:6px;justify-content:center;margin-bottom:20px}
.quiz-dot{width:28px;height:6px;border-radius:3px;background:var(--surface3);transition:all .3s}
.quiz-dot.correct{background:var(--success)}
.quiz-dot.wrong{background:var(--primary)}
.quiz-dot.current{background:var(--secondary)}
.quiz-question{text-align:center;margin-bottom:20px}
.quiz-question .q-char{font-size:56px;font-weight:700}
/* Grammar cards */
.grammar-level-section{margin-bottom:20px}
.grammar-level-title{font-size:16px;font-weight:700;margin:16px 0 8px;color:var(--text);padding-bottom:4px;border-bottom:2px solid var(--primary)}
.grammar-card{cursor:pointer;margin-bottom:8px;transition:all .2s}
.grammar-card:hover{border-color:var(--primary)}
.grammar-header{display:flex;align-items:center;gap:12px;padding:14px 18px}
.grammar-pattern{font-size:16px;font-weight:700;color:var(--secondary);font-family:'KaiTi','楷体',serif}
.grammar-en{font-size:12px;color:var(--text3);flex:1}
.grammar-arrow{font-size:10px;color:var(--text3);transition:transform .3s}
.grammar-body{display:none;padding:0 18px 16px;border-top:1px solid var(--surface3)}
.grammar-explain{font-size:14px;color:var(--text2);line-height:1.8;margin-bottom:12px}
.grammar-examples{display:flex;flex-direction:column;gap:6px}
.grammar-ex{font-size:13px;color:var(--text);background:var(--surface);padding:8px 12px;border-radius:6px;border-left:3px solid var(--secondary);line-height:1.6}
/* Filter & mode buttons */
.grammar-filter-btn.active,.quiz-mode-btn.active{background:var(--primary)!important;color:#fff!important;border-color:var(--primary)!important}
#searchAllBtn{transition:all .2s}
/* Tone quiz */
.tone-correct{background:#4caf50!important;color:#fff!important;border-color:#4caf50!important}
.tone-wrong{background:#e74c3c!important;color:#fff!important;border-color:#e74c3c!important}
/* Stroke animation */
.char-stroke-box.done{opacity:.5;background:rgba(194,59,34,.05)}
#strokeAnimCanvas{transition:all .3s}
.quiz-question .q-hint{color:var(--text3);font-size:14px}
.quiz-options{display:grid;gap:8px}
.quiz-opt{
  padding:14px 18px;border-radius:10px;border:1px solid rgba(0,0,0,.06);
  background:var(--surface);color:var(--text);
  font-family:'Inter','Noto Sans SC',sans-serif;
  font-size:17px;cursor:pointer;transition:all .2s;text-align:left;
}
.quiz-opt:hover{border-color:var(--secondary);background:rgba(74,108,247,.04)}
.quiz-opt.correct{border-color:var(--success);background:rgba(16,185,129,.06)}
.quiz-opt.wrong{border-color:var(--primary);background:rgba(233,78,78,.06);color:var(--primary);text-decoration:line-through}
.quiz-opt:disabled{cursor:default;opacity:.7}

/* ===== VOCAB TABLE ===== */
.vocab-table{width:100%;border-collapse:collapse;font-size:14px}
.vocab-table th{
  padding:10px 14px;text-align:left;font-weight:600;font-size:12px;
  color:var(--text3);border-bottom:1px solid var(--surface3);
  position:sticky;top:0;background:var(--surface);
}
.vocab-table td{padding:10px 14px;border-bottom:1px solid rgba(0,0,0,.03)}
.vocab-table tr:hover td{background:rgba(74,108,247,.02)}
.vocab-table .v-hanzi{font-size:18px;font-weight:500}
.vocab-table .v-pinyin{color:var(--secondary);font-size:13px}
.vocab-table .v-meaning{color:var(--text2)}
.vocab-table .v-hsk{font-size:11px;padding:2px 8px;border-radius:10px;font-weight:600}
.vocab-search{
  width:100%;padding:10px 16px;border-radius:10px;border:1px solid rgba(0,0,0,.08);
  font-family:inherit;font-size:14px;background:var(--surface);color:var(--text);
  margin-bottom:12px;transition:border-color .2s;
}
.vocab-search:focus{outline:none;border-color:var(--secondary);box-shadow:0 0 0 3px rgba(74,108,247,.1)}

/* ===== FLASHCARD ===== */
.flashcard-wrap{padding:20px 0}
.flashcard{
  width:100%;max-width:480px;height:300px;margin:0 auto;perspective:1000px;cursor:pointer;
}
.flashcard-inner{
  position:relative;width:100%;height:100%;
  transition:transform .6s cubic-bezier(.4,0,.2,1);transform-style:preserve-3d;
}
.flashcard.flipped .flashcard-inner{transform:rotateY(180deg)}
.flashcard-face{
  position:absolute;inset:0;border-radius:var(--radius-lg);
  display:flex;flex-direction:column;align-items:center;justify-content:center;
  backface-visibility:hidden;padding:32px;
  background:linear-gradient(145deg,var(--surface),#faf8ff);
  border:1px solid rgba(0,0,0,.04);box-shadow:var(--shadow-lg);
}
.flashcard-back{transform:rotateY(180deg)}
.flashcard .fc-big{font-size:72px;font-weight:300;margin-bottom:12px}
.flashcard .fc-hint{color:var(--text3);font-size:14px}
.flashcard .fc-pinyin{font-size:24px;color:var(--secondary);font-weight:500}
.flashcard .fc-meaning{font-size:18px;color:var(--text2);margin-top:6px}

/* ===== CHECK-IN ===== */
.checkin-card{text-align:center;padding:32px}
.checkin-card .streak-num{font-size:52px;font-weight:900;color:var(--primary)}
.checkin-card .streak-label{color:var(--text3);margin-bottom:16px}
.week-grid{display:flex;gap:8px;justify-content:center;margin:16px 0}
.week-day{
  width:40px;height:40px;border-radius:50%;display:flex;align-items:center;justify-content:center;
  font-size:14px;font-weight:600;background:var(--surface3);color:var(--text3);
}
.week-day.done{background:var(--success);color:#fff}
.week-day.today{background:var(--primary);color:#fff}

/* ===== PROFILE ===== */
.profile-banner{display:flex;align-items:center;gap:24px;padding:32px;background:linear-gradient(135deg,var(--surface),var(--surface2));border-radius:16px;margin-bottom:24px;border:1px solid rgba(0,0,0,.04)}
.ph-avatar-lg{width:80px;height:80px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--accent));display:flex;align-items:center;justify-content:center;font-size:36px;color:#fff;font-weight:700;flex-shrink:0;box-shadow:0 4px 16px rgba(194,59,34,.25)}
.ph-info{flex:1}
.ph-info .ph-name{font-size:22px;font-weight:700;margin-bottom:4px}
.ph-info .ph-joined{font-size:13px;color:var(--text3);margin-bottom:8px}
.ph-info .ph-level{font-size:13px;color:var(--secondary);background:var(--secondary-light);display:inline-block;padding:4px 12px;border-radius:20px}
.ph-logout-btn{padding:8px 16px;font-size:13px;border:1px solid var(--primary);border-radius:8px;background:none;color:var(--primary);cursor:pointer;font-family:inherit;transition:all .2s;flex-shrink:0}
.ph-logout-btn:hover{background:var(--primary);color:#fff}
.profile-stats{display:grid;grid-template-columns:repeat(4,1fr);gap:16px;margin-bottom:24px}
@media(max-width:768px){.profile-stats{grid-template-columns:repeat(2,1fr)}}
.profile-stat{text-align:center;padding:24px 16px;border-radius:16px;background:var(--surface);border:1px solid rgba(0,0,0,.04);transition:all .2s}
.profile-stat:hover{transform:translateY(-2px);box-shadow:var(--shadow)}
.profile-stat .ps-icon{font-size:28px;margin-bottom:8px}
.profile-stat .ps-num{font-size:32px;font-weight:800;background:linear-gradient(135deg,var(--primary),var(--accent));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.profile-stat .ps-label{font-size:12px;color:var(--text3);margin-top:4px;overflow-wrap:break-word}
.profile-stat.streak .ps-num{background:linear-gradient(135deg,#f59e0b,#d97706);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.profile-stat.words .ps-num{background:linear-gradient(135deg,var(--secondary),#7eb8da);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.profile-stat.quizzes .ps-num{background:linear-gradient(135deg,#8b5cf6,#7c3aed);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.profile-stat.checkins .ps-num{background:linear-gradient(135deg,var(--success),#5c9a6b);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.profile-grid{display:grid;grid-template-columns:1fr 1fr;gap:20px}
@media(max-width:768px){.profile-grid{grid-template-columns:1fr}}
.profile-col{display:flex;flex-direction:column;gap:20px}
.acc-grid{display:flex;flex-direction:column;gap:0}
.acc-item{display:flex;justify-content:space-between;align-items:center;padding:14px 0;border-bottom:1px solid var(--surface3)}
.acc-item:last-child{border-bottom:none}
.acc-label{font-size:13px;color:var(--text3)}
.acc-value{font-size:15px;font-weight:600;color:var(--text)}
.tips-list{display:flex;flex-direction:column;gap:12px}
.tip-item{display:flex;align-items:flex-start;gap:10px;font-size:14px;color:var(--text2);line-height:1.6}
.tip-icon{flex-shrink:0;margin-top:1px}
.empty-state{text-align:center;padding:32px 16px;color:var(--text3);font-size:14px}
.progress-bar{height:8px;background:var(--surface3);border-radius:4px;overflow:hidden}
.progress-fill{height:100%;background:linear-gradient(90deg,var(--secondary),var(--accent));border-radius:4px;transition:width .6s ease}
.streak-dots{display:flex;gap:8px}
.streak-dot{width:32px;height:32px;border-radius:50%;display:flex;align-items:center;justify-content:center;font-size:12px;background:var(--surface2);color:var(--text3)}
.streak-dot.checked{background:linear-gradient(135deg,var(--success),#5c9a6b);color:#fff}
.streak-dot.today{border:2px solid var(--secondary)}
.profile-header{display:none}

/* ===== BACK TO TOP BUTTON ===== */
.back-to-top{
  position:fixed;bottom:90px;right:90px;z-index:800;
  width:44px;height:44px;border-radius:50%;
  background:var(--surface);border:1px solid var(--surface3);
  color:var(--text2);font-size:20px;cursor:pointer;
  box-shadow:var(--shadow);transition:all .3s cubic-bezier(.4,0,.2,1);
  display:flex;align-items:center;justify-content:center;
  opacity:0;transform:translateY(20px) scale(.8);pointer-events:none;
}
.back-to-top.visible{opacity:1;transform:translateY(0) scale(1);pointer-events:auto}
.back-to-top:hover{background:var(--primary);color:#fff;border-color:var(--primary);transform:translateY(-3px);box-shadow:0 6px 20px rgba(194,59,34,.3)}
.back-to-top.visible:hover{transform:translateY(-3px) scale(1)}

/* ===== LOADING SPINNER ===== */
.spinner-container{display:flex;flex-direction:column;align-items:center;justify-content:center;padding:40px 20px;gap:12px}
.spinner{width:36px;height:36px;border:3px solid var(--surface3);border-top-color:var(--primary);border-radius:50%;animation:spin .7s linear infinite}
@keyframes spin{to{transform:rotate(360deg)}}
.spinner-text{font-size:13px;color:var(--text3);animation:pulseText 1.5s ease infinite}
@keyframes pulseText{0%,100%{opacity:.6}50%{opacity:1}}

/* ===== AI CHAT ===== */



@keyframes msgIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}
.toast{
  padding:12px 20px;border-radius:12px;background:var(--surface);
  box-shadow:var(--shadow-lg);border:1px solid rgba(0,0,0,.06);
  font-size:14px;font-weight:500;animation:slideIn .3s ease;
  display:flex;align-items:center;gap:10px;max-width:360px;
}
.toast.success{border-left:4px solid var(--success)}
.toast.error{border-left:4px solid var(--primary)}
.toast.info{border-left:4px solid var(--secondary)}
@keyframes slideIn{from{opacity:0;transform:translateX(40px)}to{opacity:1;transform:translateX(0)}}
.toast-container{position:fixed;top:16px;left:50%;transform:translateX(-50%);z-index:9999;display:flex;flex-direction:column;gap:8px;pointer-events:none}
.toast{pointer-events:auto}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar{width:5px}
::-webkit-scrollbar-track{background:transparent}
::-webkit-scrollbar-thumb{background:var(--surface3);border-radius:4px}

/* ===== LOADING ===== */
.loading-dots::after{content:'';animation:dots 1.5s steps(4,end) infinite}
@keyframes dots{0%{content:''}25%{content:'.'}50%{content:'..'}75%{content:'...'}}

/* ===== MOBILE ===== */
.mobile-toggle{
  display:none;position:fixed;bottom:20px;right:86px;z-index:200;
  width:48px;height:48px;border-radius:50%;
  background:linear-gradient(135deg,var(--primary),var(--accent));
  color:#fff;border:none;font-size:20px;cursor:pointer;
  box-shadow:0 4px 20px rgba(233,78,78,.4);
}
@media(max-width:768px){
  .sidebar{position:fixed;left:0;top:0;z-index:150;transform:translateX(-100%)}
  .sidebar.open{transform:translateX(0);box-shadow:0 0 0 100vw rgba(0,0,0,.3)}
  .sidebar-overlay{display:none;position:fixed;inset:0;z-index:140;background:rgba(0,0,0,.3)}
  .sidebar-overlay.show{display:block}
  .mobile-toggle{display:flex;align-items:center;justify-content:center}
  .main{padding-top:16px}
  .page{padding:20px 16px 80px}
  .page-header h2{font-size:22px}}

/* ===== LOGIN MODAL ===== */
.modal-overlay{position:fixed;inset:0;z-index:1000;background:rgba(0,0,0,.5);display:flex;align-items:center;justify-content:center;animation:fadeIn .25s ease}
.modal{background:var(--surface);border-radius:var(--radius-lg);padding:0;width:400px;max-width:90vw;box-shadow:0 20px 60px rgba(0,0,0,.2);animation:slideUp .3s ease}
.modal-header{display:flex;align-items:center;justify-content:space-between;padding:20px 24px;border-bottom:1px solid var(--surface2)}
.modal-header h2{font-size:18px;font-weight:700}
.modal-close{width:32px;height:32px;border-radius:50%;border:none;background:var(--surface2);cursor:pointer;font-size:16px;display:flex;align-items:center;justify-content:center;color:var(--text2);transition:all .2s}
.modal-close:hover{background:var(--surface3)}
.modal-body{padding:24px}
.form-group{margin-bottom:16px}
.form-group label{display:block;font-size:13px;font-weight:600;color:var(--text2);margin-bottom:4px}
.form-input{width:100%;padding:10px 14px;border-radius:10px;border:1px solid rgba(0,0,0,.08);font-family:inherit;font-size:14px;background:var(--surface2);color:var(--text);outline:none;transition:border-color .2s}
.form-input:focus{border-color:var(--secondary);box-shadow:0 0 0 3px rgba(74,108,247,.1)}
.form-error{color:var(--primary);font-size:13px;margin-bottom:12px;display:none}
.login-btn-sidebar{width:100%;padding:8px 14px;border-radius:10px;border:1px solid rgba(0,0,0,.06);background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;cursor:pointer;font-family:inherit;font-size:14px;font-weight:600;transition:all .2s;display:flex;align-items:center;gap:8px}
.login-btn-sidebar:hover{transform:translateY(-1px);box-shadow:0 4px 12px rgba(233,78,78,.3)}
.user-info-sidebar{display:flex;align-items:center;gap:8px;padding:8px 14px;border-radius:10px;background:var(--surface2);font-size:13px}
.user-info-sidebar .avatar{width:28px;height:28px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--accent));display:flex;align-items:center;justify-content:center;color:#fff;font-size:12px;font-weight:700}
.user-info-sidebar .logout-btn{margin-left:auto;background:none;border:none;color:var(--text3);cursor:pointer;font-size:12px;padding:4px 8px;border-radius:6px}
.user-info-sidebar .logout-btn:hover{background:var(--surface3);color:var(--primary)}

.hidden{display:none!important}

/* Language switcher */
.lang-switch{display:flex;gap:2px;padding:8px 14px;border-bottom:1px solid var(--surface3)}
.lang-option{padding:4px 10px;border-radius:4px;border:none;cursor:pointer;font-size:11px;font-weight:600;font-family:var(--font-body);background:transparent;color:var(--text3);transition:all .2s}
.lang-option:hover{color:var(--text);background:var(--surface2)}
.lang-option.active{background:var(--primary);color:var(--surface);font-family:var(--font-title)}
/* ===== CHAT SIDEBAR (right) ===== */
.chat-overlay{
  position:fixed;inset:0;z-index:899;background:rgba(0,0,0,.3);
  display:none;
}
.chat-overlay.open{display:block}
.chat-sidebar-toggle{
  position:fixed;bottom:28px;right:28px;z-index:901;
  width:46px;height:46px;border-radius:50%;
  background:linear-gradient(135deg,var(--secondary),var(--accent));
  color:#fff;border:none;font-size:18px;font-weight:700;
  font-family:'Noto Serif SC','Ma Shan Zheng',serif;
  cursor:pointer;
  box-shadow:0 3px 16px rgba(74,108,247,.25);
  transition:all .4s cubic-bezier(.4,0,.2,1);
  display:flex;align-items:center;justify-content:center;
  animation:aiFloat 4s ease-in-out infinite;
}
.chat-sidebar-toggle::after{
  content:'';position:absolute;inset:4px;
  border-radius:50%;
  border:1.5px solid rgba(255,255,255,.2);
  pointer-events:none;
  transition:opacity .4s;
}
.chat-sidebar-toggle:hover{
  transform:scale(1.1);
  box-shadow:0 6px 24px rgba(74,108,247,.4);
}
.chat-sidebar-toggle:hover::after{
  border-color:rgba(255,255,255,.4);
}
.chat-sidebar-toggle.hidden{
  opacity:0;pointer-events:none;
  transform:scale(.7);
  animation:none;
}
.chat-sidebar-toggle.hidden::after{opacity:0}
@keyframes aiFloat{
  0%,100%{transform:translateY(0)}
  50%{transform:translateY(-5px)}
}
.chat-sidebar{
  position:fixed;top:0;right:-400px;z-index:900;
  width:400px;max-width:90vw;height:100vh;
  background:var(--surface);border-left:3px solid #2563eb;
  display:flex;flex-direction:column;overflow:hidden;
  transition:right .3s cubic-bezier(.4,0,.2,1);
  box-shadow:-4px 0 40px rgba(37,99,235,.08);
}
.chat-sidebar.open{right:0}
.chat-sidebar-header{
  padding:16px 20px;border-bottom:1px solid var(--surface2);
  background:linear-gradient(135deg,#eff6ff,#dbeafe);
  display:flex;align-items:center;justify-content:space-between;
  font-size:15px;font-weight:700;color:#1e40af;flex-shrink:0;
}
.chat-sidebar-header button{
  width:32px;height:32px;border-radius:50%;border:none;
  background:rgba(37,99,235,.1);cursor:pointer;font-size:16px;
  display:flex;align-items:center;justify-content:center;
  color:#2563eb;transition:all .2s;
}
.chat-sidebar-header button:hover{background:rgba(37,99,235,.2);color:#1e40af}
.chat-clear-btn{font-size:14px!important}
.chat-messages{
  flex:1;min-height:0;overflow-y:scroll;overflow-x:hidden;padding:16px;display:flex;flex-direction:column;gap:10px;
}
.chat-messages::-webkit-scrollbar{width:4px}
.chat-messages::-webkit-scrollbar-track{background:transparent}
.chat-messages::-webkit-scrollbar-thumb{background:rgba(37,99,235,.2);border-radius:2px}
.chat-msg{
  max-width:85%;padding:10px 14px;border-radius:14px;
  font-size:14px;line-height:1.7;animation:msgIn .25s ease;
  word-break:break-word;overflow-wrap:break-word;
}
.chat-msg.user{
  align-self:flex-end;background:linear-gradient(135deg,#2563eb,#4a90d9);color:#fff;
  border-bottom-right-radius:4px;
}
.chat-msg.assistant{
  align-self:flex-start;background:var(--surface2);
  border-bottom-left-radius:4px;border:1px solid #e0e7ff;
}
.chat-msg .msg-typing::after{content:'▊';animation:blink 1s steps(2) infinite;color:#2563eb}
@keyframes blink{0%{opacity:1}50%{opacity:0}}
.chat-input-area{
  padding:12px 16px;border-top:1px solid var(--surface2);
  background:linear-gradient(0deg,#eff6ff,transparent);
  display:flex;gap:8px;align-items:flex-end;flex-shrink:0;
}
.chat-input-area textarea{
  flex:1;border:1px solid #bfdbfe;border-radius:12px;
  padding:10px 14px;font-family:inherit;font-size:14px;
  resize:none;outline:none;background:var(--surface);
  max-height:100px;line-height:1.5;color:var(--text);
  transition:border-color .2s;
}
.chat-input-area textarea:focus{border-color:#2563eb;box-shadow:0 0 0 3px rgba(37,99,235,.1)}
.chat-send-btn{
  width:38px;height:38px;border-radius:10px;border:none;
  background:linear-gradient(135deg,#2563eb,#4a90d9);color:#fff;cursor:pointer;
  font-size:16px;display:flex;align-items:center;justify-content:center;
  transition:all .2s;flex-shrink:0;
  box-shadow:0 2px 8px rgba(37,99,235,.25);
}
.chat-send-btn:hover{background:linear-gradient(135deg,#1d4ed8,#2563eb);transform:scale(1.05)}
.chat-send-btn:disabled{opacity:.4;cursor:default;transform:none}
.chat-msg.error{background:rgba(233,78,78,.08);color:var(--primary);align-self:center;font-size:13px;max-width:90%}

/* ===== TRANSLATE PAGE ===== */
.translate-card{
  background:var(--surface);border:1px solid var(--surface3);border-radius:var(--radius-lg);
  padding:24px;box-shadow:var(--shadow)
}
.translate-row{display:flex;gap:16px;align-items:stretch}
.translate-col{flex:1;display:flex;flex-direction:column;min-width:0}
.translate-lang-select{
  width:100%;padding:10px 12px;border-radius:var(--radius);border:1px solid var(--surface3);
  background:var(--surface2);color:var(--text);font-family:inherit;font-size:14px;
  cursor:pointer;outline:none;margin-bottom:10px;transition:border-color .2s
}
.translate-lang-select:focus{border-color:var(--accent)}
.translate-textarea{
  width:100%;min-height:160px;padding:14px;border-radius:var(--radius);
  border:1px solid var(--surface3);background:var(--bg);color:var(--text);
  font-family:inherit;font-size:15px;line-height:1.7;resize:vertical;outline:none;
  transition:border-color .2s;box-sizing:border-box
}
.translate-textarea:focus{border-color:var(--accent)}
.translate-output{background:var(--surface2)!important;cursor:default}
.translate-char-count{text-align:right;font-size:11px;color:var(--text3);padding:4px 4px 0}
.translate-swap{
  display:flex;align-items:center;justify-content:center;font-size:28px;cursor:pointer;
  color:var(--accent);user-select:none;padding:0 4px;transition:transform .2s,color .2s;
  flex-shrink:0;width:40px
}
.translate-swap:hover{transform:rotate(180deg);color:var(--primary)}
.translate-actions{display:flex;gap:8px;margin-top:10px;flex-wrap:wrap}
.translate-status{
  margin-top:12px;padding:10px 14px;border-radius:var(--radius);font-size:13px;
  min-height:20px;display:none
}
.translate-status.loading{display:flex;align-items:center;gap:8px;color:var(--text3)}
.translate-status.error{display:flex;align-items:center;gap:8px;color:var(--primary);background:rgba(194,59,34,.06)}
.translate-status.done{display:none}
.translate-spinner{width:16px;height:16px;border:2px solid var(--surface3);border-top-color:var(--accent);border-radius:50%;animation:spin .6s linear infinite}
@media(max-width:768px){
  .translate-row{flex-direction:column}
  .translate-swap{transform:rotate(90deg);height:32px}
  .translate-swap:hover{transform:rotate(270deg)}
}

/* ===== PREMIUM ENHANCEMENTS ===== */
/* Glassmorphism cards on hover */
.card,.level-btn,.feature-card,.profile-stat,.translate-card{
  transition:all .3s cubic-bezier(.4,0,.2,1),background-color .35s ease;
}
.card:hover,.translate-card:hover{
  box-shadow:var(--shadow-lg),0 0 0 1px rgba(200,155,60,.06);
}
/* Card subtle gradient border on hover */
.feature-card::after{
  content:'';position:absolute;inset:0;border-radius:inherit;
  background:linear-gradient(135deg,var(--accent),transparent 50%);
  opacity:0;transition:opacity .4s;pointer-events:none;
  z-index:0;
}
.feature-card{position:relative}
.feature-card>*{position:relative;z-index:1}
.feature-card:hover::after{opacity:.06}
/* Skeleton loading shimmer */
@keyframes shimmer{
  0%{background-position:-200% 0}
  100%{background-position:200% 0}
}
.skeleton{
  background:linear-gradient(90deg,var(--surface2) 25%,var(--surface) 50%,var(--surface2) 75%);
  background-size:200% 100%;
  animation:shimmer 1.5s ease infinite;
  border-radius:6px;color:transparent!important;
}
/* Vocab table row hover - smoother */
.vocab-table tbody tr{
  transition:background .2s;
}
.vocab-table tbody tr:hover td{
  background:rgba(200,155,60,.04);
}
/* Nav item active - smoother transition */
.nav-item{
  transition:all .25s cubic-bezier(.4,0,.2,1),border-left-color .3s ease;
}
.nav-item.active{
  background:linear-gradient(135deg,rgba(194,59,34,.08),rgba(200,155,60,.08));
  border-left-width:3px;
}
/* Page transition - smooth with will-change */
.page{
  will-change:opacity,transform;
}
/* Hero subtle background animation */
.hero{
  background-size:200% 200%;
  animation:heroBg 15s ease infinite alternate;
}
@keyframes heroBg{
  0%{background-position:0% 0%}
  100%{background-position:100% 100%}
}
/* Profile stat hover - more premium */
.profile-stat:hover{
  transform:translateY(-3px);
  box-shadow:var(--shadow-lg);
  border-color:rgba(200,155,60,.15);
}
/* Flashcard shadow refinement */
.flashcard-face{
  box-shadow:0 8px 32px rgba(44,44,44,.1),0 2px 8px rgba(44,44,44,.06);
}
/* Better focus styles for accessibility */
button:focus-visible,.btn:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{
  outline:2px solid var(--accent);
  outline-offset:2px;
}
/* Scrolling experience - smoother */
html{scroll-behavior:smooth}
body{-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}
/* Mobile back-to-top refinement */
@media(max-width:768px){
  .back-to-top{bottom:80px;right:16px;width:40px;height:40px}
}