/* ===== Variables ===== */
:root {
  --bg: #f4f6fb;
  --bg-dot: #e2e5f1;
  --surface: rgba(255,255,255,.75);
  --surface-solid: #fff;
  --surface-hover: rgba(255,255,255,.92);
  --text: #0f182a;
  --text2: #4a5578;
  --text3: #909bb8;
  --primary: #6366f1;
  --primary2: #a855f7;
  --primary3: #d946ef;
  --primary-dim: rgba(99,102,241,.1);
  --primary-glow: rgba(99,102,241,.25);
  --border: rgba(15,23,42,.08);
  --success: #22c55e;
  --error: #ef4444;
  --shadow: 0 1px 3px rgba(0,0,0,.05);
  --shadow-lg: 0 8px 40px rgba(0,0,0,.07);
  --radius: 16px;
  --radius-sm: 10px;
  --radius-xs: 7px;
  --nav-h: 64px;
  --max-w: 1040px;
  --font: 'Inter',-apple-system,BlinkMacSystemFont,sans-serif;
  --transition: 0.3s cubic-bezier(.22,1,.36,1);
}
.dark {
  --bg: #080c1a;
  --bg-dot: #131b33;
  --surface: rgba(18,24,47,.75);
  --surface-solid: #12182f;
  --surface-hover: rgba(25,33,58,.85);
  --text: #eef1ff;
  --text2: #8b95b8;
  --text3: #555d7a;
  --primary-dim: rgba(99,102,241,.13);
  --primary-glow: rgba(99,102,241,.3);
  --border: rgba(255,255,255,.06);
  --shadow: 0 1px 3px rgba(0,0,0,.2);
  --shadow-lg: 0 8px 40px rgba(0,0,0,.5);
}

/* ===== Reset ===== */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:var(--font);
  background:var(--bg);
  color:var(--text);
  line-height:1.6;
  padding-top:var(--nav-h);
  transition:background var(--transition),color var(--transition);
  -webkit-font-smoothing:antialiased;
  background-image:radial-gradient(var(--bg-dot) 1px,transparent 0);
  background-size:32px 32px;
}
a{color:var(--primary);text-decoration:none}
::selection{background:var(--primary);color:#fff}

/* Scrollbar */
::-webkit-scrollbar{width:6px}
::-webkit-scrollbar-track{background:transparent}
::-webkit-scrollbar-thumb{background:var(--text3);border-radius:3px}
::-webkit-scrollbar-thumb:hover{background:var(--text2)}

/* ===== Buttons ===== */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  padding:10px 24px;border-radius:var(--radius-sm);
  border:1px solid var(--border);
  background:var(--surface);color:var(--text);
  cursor:pointer;font-size:14px;font-weight:500;
  font-family:var(--font);
  transition:all var(--transition);
  backdrop-filter:blur(12px);
  user-select:none;
}
.btn:hover{
  background:var(--surface-hover);
  border-color:var(--text3);
  transform:translateY(-2px);
  box-shadow:var(--shadow);
}
.btn-primary{
  background:linear-gradient(135deg,var(--primary),var(--primary2),var(--primary3));
  color:#fff;border:none;
  box-shadow:0 4px 20px var(--primary-glow);
  position:relative;
  overflow:hidden;
}
.btn-primary::after{
  content:'';position:absolute;inset:0;
  background:linear-gradient(135deg,transparent 40%,rgba(255,255,255,.15) 50%,transparent 60%);
  transition:transform .5s;
  transform:translateX(-100%);
}
.btn-primary:hover::after{transform:translateX(100%)}
.btn-primary:hover{
  box-shadow:0 6px 28px var(--primary-glow);
  transform:translateY(-3px);
}
.btn-lg{padding:14px 32px;font-size:16px;border-radius:var(--radius)}
.btn-sm{padding:6px 14px;font-size:12px;border-radius:var(--radius-xs)}
.btn-danger{background:var(--error);color:#fff;border:none}
.btn-danger:hover{opacity:.9;transform:translateY(-1px)}

/* ===== Navbar ===== */
.navbar{
  position:fixed;top:0;left:0;right:0;z-index:100;
  height:var(--nav-h);
  background:var(--surface);
  border-bottom:1px solid var(--border);
  backdrop-filter:blur(20px);
  -webkit-backdrop-filter:blur(20px);
  transition:background var(--transition);
}
.navbar::after{
  content:'';position:absolute;bottom:-1px;left:10%;right:10%;
  height:1px;
  background:linear-gradient(90deg,transparent,var(--primary-glow),transparent);
  opacity:.5;
}
.nav-inner{
  max-width:var(--max-w);margin:0 auto;padding:0 24px;
  display:flex;align-items:center;height:100%;gap:24px;
}
.nav-logo{
  font-weight:800;font-size:20px;
  background:linear-gradient(135deg,var(--primary),var(--primary2),var(--primary3));
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;
  white-space:nowrap;
  letter-spacing:-.3px;
}
.nav-center{display:flex;gap:4px;flex:1}
.nav-center a{
  color:var(--text2);font-size:14px;font-weight:500;
  transition:all var(--transition);
  padding:6px 16px;border-radius:var(--radius-xs);
  position:relative;
}
.nav-center a:hover{color:var(--text);background:var(--primary-dim)}
.nav-center a.active{
  color:var(--primary);
  background:var(--primary-dim);
  font-weight:600;
}
.nav-right{display:flex;align-items:center;gap:16px;flex-shrink:0}
.nav-progress{display:flex;align-items:center;gap:10px;font-size:12px;color:var(--text2)}
.progress-track{
  width:90px;height:6px;
  background:var(--border);
  border-radius:3px;overflow:hidden;
}
.progress-track.lg{width:100%;max-width:300px;height:12px;border-radius:6px}
.progress-fill{
  height:100%;
  background:linear-gradient(90deg,var(--primary),var(--primary2),var(--primary3));
  border-radius:3px;
  transition:width .8s cubic-bezier(.22,1,.36,1);
  width:0%;
}
#themeToggle{
  background:var(--primary-dim);
  border:none;border-radius:var(--radius-xs);
  width:36px;height:36px;
  cursor:pointer;font-size:16px;
  transition:all var(--transition);
  display:flex;align-items:center;justify-content:center;
}
#themeToggle:hover{background:var(--border);transform:scale(1.1)}

/* Hamburger */
.hamburger{
  display:none;background:none;border:none;
  cursor:pointer;padding:8px;
  flex-direction:column;gap:5px;
}
.hamburger span{
  display:block;width:22px;height:2px;
  background:var(--text);
  border-radius:2px;
  transition:all .3s;
  transform-origin:center;
}
.hamburger.open span:nth-child(1){transform:translateY(7px) rotate(45deg)}
.hamburger.open span:nth-child(2){opacity:0}
.hamburger.open span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

/* ===== Sections ===== */
.section{
  display:none;
  max-width:var(--max-w);
  margin:0 auto;
  padding:40px 24px 60px;
}
.section.active{
  display:block;
  animation:fadeUp .5s ease;
}
@keyframes fadeUp{
  from{opacity:0;transform:translateY(24px)}
  to{opacity:1;transform:translateY(0)}
}
@keyframes fadeIn{from{opacity:0}to{opacity:1}}
@keyframes pulse{0%,100%{opacity:1}50%{opacity:.6}}
.sec-header{margin-bottom:32px}
.sec-header h2{font-size:28px;font-weight:700;margin-bottom:6px}
.sec-header p{color:var(--text2);font-size:15px}

/* ===== Hero ===== */
.hero{
  position:relative;
  text-align:center;
  padding:80px 0 50px;
  overflow:hidden;
}
.hero-bg{
  position:absolute;top:-50%;left:-50%;
  width:200%;height:200%;
  pointer-events:none;
}
.hero-bg::before,.hero-bg::after{
  content:'';position:absolute;
  border-radius:50%;
  animation:heroFloat 8s ease-in-out infinite;
}
.hero-bg::before{
  width:400px;height:400px;
  background:radial-gradient(circle,rgba(99,102,241,.12),transparent 70%);
  top:20%;left:30%;
}
.hero-bg::after{
  width:300px;height:300px;
  background:radial-gradient(circle,rgba(168,85,247,.1),transparent 70%);
  bottom:10%;right:20%;
  animation-delay:-4s;
}
@keyframes heroFloat{
  0%,100%{transform:translate(0,0) scale(1)}
  33%{transform:translate(30px,-30px) scale(1.05)}
  66%{transform:translate(-20px,20px) scale(.95)}
}
.hero-content{position:relative;z-index:1}
.hero-badge{
  display:inline-block;
  padding:4px 16px;
  border-radius:20px;
  background:var(--primary-dim);
  color:var(--primary);
  font-size:12px;font-weight:600;
  margin-bottom:16px;
  letter-spacing:.5px;
}
.hero h1{
  font-size:38px;font-weight:800;
  line-height:1.15;
  margin-bottom:16px;
  letter-spacing:-.5px;
}
.hero-desc{
  color:var(--text2);
  font-size:16px;
  max-width:600px;
  margin:0 auto 32px;
  line-height:1.7;
}
.hero-stats{
  display:flex;justify-content:center;
  gap:48px;margin-top:48px;
}
.stat{text-align:center}
.stat-num{
  display:block;
  font-size:32px;font-weight:800;
  background:linear-gradient(135deg,var(--primary),var(--primary2));
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;
}
.stat-label{font-size:13px;color:var(--text3);margin-top:2px;font-weight:500}
.pulse{animation:pulse 2s ease infinite}

/* ===== Cards ===== */
.card-grid{
  display:grid;
  grid-template-columns:repeat(auto-fill,minmax(300px,1fr));
  gap:16px;
}
.card{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:22px 22px 22px 60px;
  cursor:pointer;
  transition:all .35s cubic-bezier(.22,1,.36,1);
  position:relative;
  backdrop-filter:blur(12px);
  overflow:hidden;
}
.card::before{
  content:'';
  position:absolute;inset:0;
  border-radius:var(--radius);
  opacity:0;
  transition:opacity var(--transition);
  background:linear-gradient(135deg,var(--primary-dim),transparent 60%);
  pointer-events:none;
}
.card:hover::before{opacity:1}
.card:hover{
  box-shadow:var(--shadow-lg);
  transform:translateY(-4px);
  border-color:transparent;
}
.card.done{
  border-left:3px solid var(--success);
}
.card-icon{
  position:absolute;left:20px;top:22px;
  font-size:24px;line-height:1;
}
.card-num{
  font-size:11px;font-weight:600;
  color:var(--primary);
  text-transform:uppercase;
  letter-spacing:.8px;margin-bottom:5px;
}
.card-title{
  font-size:15px;font-weight:600;
  margin-bottom:4px;
  padding-right:32px;
  line-height:1.4;
}
.card-desc{
  font-size:13px;color:var(--text2);
  line-height:1.5;
}
.card-status{
  position:absolute;top:16px;right:16px;
  font-size:16px;cursor:pointer;
  width:30px;height:30px;
  display:flex;align-items:center;justify-content:center;
  border-radius:50%;
  transition:all var(--transition);
  z-index:2;
}
.card-status:hover{
  background:var(--primary-dim);
  transform:scale(1.2);
}

/* ===== Viewer ===== */
.viewer-top{
  display:flex;align-items:center;gap:12px;
  margin-bottom:14px;flex-wrap:wrap;
}
.viewer-top h3{flex:1;font-size:18px;font-weight:600;min-width:150px}
.viewer-actions{display:flex;align-items:center;gap:10px}
.breadcrumb{
  font-size:12px;color:var(--text3);
  background:var(--primary-dim);
  padding:3px 12px;border-radius:20px;
}
.viewer-controls{
  display:flex;align-items:center;gap:14px;
  justify-content:center;margin-bottom:16px;
  font-size:13px;color:var(--text2);
}
.viewer-pos{font-weight:600;min-width:80px;text-align:center}
.viewer-container{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  min-height:400px;
  position:relative;
}
.viewer-pages{
  padding:20px;
  display:flex;flex-direction:column;
  align-items:center;gap:18px;
}
.viewer-loading{
  display:flex;flex-direction:column;
  align-items:center;justify-content:center;
  gap:18px;min-height:400px;
  color:var(--text2);font-size:15px;
}
.spinner{
  width:36px;height:36px;
  border:3px solid var(--border);
  border-top-color:var(--primary);
  border-radius:50%;
  animation:spin .8s linear infinite;
}
@keyframes spin{to{transform:rotate(360deg)}}
.pdf-canvas{
  height:auto!important;
  border-radius:8px;
  box-shadow:0 4px 20px rgba(0,0,0,.15);
}

/* ===== Viewer Sidebar ===== */
.viewer-body{
  position:relative;display:flex;
}
.viewer-body .viewer-container{flex:1;min-width:0;overflow-x:auto}
.viewer-sidebar{
  position:absolute;top:0;z-index:5;
  width:200px;
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:12px;
  transition:width .2s,padding .2s;
}
.viewer-sidebar-left{right:100%;margin-right:8px}
.viewer-sidebar-right{left:100%;margin-left:8px}
.viewer-sidebar .sidebar-header{
  display:flex;align-items:center;justify-content:space-between;
  font-size:11px;font-weight:700;text-transform:uppercase;
  letter-spacing:.05em;color:var(--text3);
  margin-bottom:8px;padding-bottom:8px;
  border-bottom:1px solid var(--border);
}
.sidebar-toggle{
  background:none;border:none;cursor:pointer;
  font-size:9px;color:var(--text3);padding:2px 4px;
  border-radius:4px;line-height:1;
}
.sidebar-toggle:hover{background:var(--primary-dim);color:var(--text1)}
.viewer-sidebar.collapsed{
  width:28px;min-width:0;padding:12px 4px;overflow:hidden;
  border-color:transparent;
}
.viewer-sidebar.collapsed .sidebar-header{
  border-bottom:none;margin:0;padding:0;justify-content:center;
}
.viewer-sidebar.collapsed .sidebar-header span{display:none}
.viewer-sidebar.collapsed .sidebar-list{display:none}
.viewer-sidebar .sidebar-item{
  padding:8px 10px;border-radius:6px;cursor:pointer;
  font-size:12px;line-height:1.4;color:var(--text2);
  transition:background .15s,color .15s;
  margin-bottom:2px;
}
.viewer-sidebar .sidebar-item:hover{background:var(--primary-dim);color:var(--text1)}
.viewer-sidebar .sidebar-item.active{
  background:var(--primary);color:#fff;font-weight:600;
}
@media(max-width:768px){
  .viewer-sidebar{display:none}
}

/* ===== Test ===== */
#testLocked,#testReady,#testActive,#testResults{
  text-align:center;padding:40px 0;
  animation:fadeIn .4s ease;
}
.lock-icon{font-size:56px;margin-bottom:16px}
.test-start-icon{font-size:56px;margin-bottom:20px}
.test-lock-progress{
  display:flex;align-items:center;gap:12px;
  max-width:300px;margin:16px auto;
}
.test-topbar{
  display:flex;align-items:center;gap:16px;
  padding:16px 22px;
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  margin-bottom:24px;
  backdrop-filter:blur(12px);
}
.test-timer-wrap{
  position:relative;
  width:64px;height:64px;
  flex-shrink:0;
}
.timer-ring{
  position:absolute;
  top:0;left:0;
  width:100%;height:100%;
  transform:rotate(-90deg);
  transform-origin:50% 50%;
}
.timer-bg{fill:none;stroke:var(--border);stroke-width:4}
.timer-fg{
  fill:none;stroke:var(--primary);
  stroke-width:4;stroke-linecap:round;
  stroke-dasharray:163.36;
  stroke-dashoffset:0;
  transition:stroke-dashoffset 1s linear,stroke .3s;
}
.timer-fg.warning{stroke:var(--error)}
.test-timer{
  position:absolute;
  top:50%;left:50%;
  transform:translate(-50%,-50%);
  font-size:13px;font-weight:700;
  font-variant-numeric:tabular-nums;
}
.test-mid{flex:1;text-align:left}
.test-progress-bar{
  height:4px;
  background:var(--border);
  border-radius:2px;overflow:hidden;
  margin-bottom:5px;max-width:200px;
}
.test-progress-fill{
  height:100%;
  background:linear-gradient(90deg,var(--primary),var(--primary2));
  border-radius:2px;
  transition:width .3s ease;
  width:0%;
}
.test-progress-text{font-size:12px;color:var(--text2)}
.test-type{
  display:inline-block;
  padding:5px 18px;
  border-radius:20px;
  font-size:13px;font-weight:600;
  margin-bottom:16px;
  background:var(--primary-dim);
  color:var(--primary);
}
.test-question{
  font-size:18px;font-weight:600;
  margin-bottom:22px;line-height:1.5;
  max-width:700px;margin-left:auto;margin-right:auto;
}
.test-options{max-width:600px;margin:0 auto 24px;text-align:left}
.test-opt{
  display:flex;align-items:flex-start;gap:12px;
  padding:14px 20px;margin-bottom:8px;
  border:1px solid var(--border);
  border-radius:var(--radius-sm);
  cursor:pointer;
  transition:all var(--transition);
  font-size:14px;
  background:var(--surface);
}
.test-opt:hover{border-color:var(--primary);background:var(--primary-dim);transform:translateX(4px)}
.test-opt.selected{
  background:linear-gradient(135deg,var(--primary),var(--primary2));
  color:#fff;border-color:transparent;
  transform:translateX(4px);
}
.test-opt.selected .opt-label{color:rgba(255,255,255,.7)}
.test-opt .opt-label{font-weight:600;min-width:22px;color:var(--text2)}

/* Matching */
.test-matching{max-width:640px;margin:0 auto 24px}
.matching-cols{display:grid;grid-template-columns:1fr 1fr;gap:24px;align-items:start}
.matching-left,.matching-right{display:flex;flex-direction:column;gap:8px}
.match-item{
  padding:12px 16px;
  border:1px solid var(--border);
  border-radius:var(--radius-sm);
  cursor:pointer;
  transition:all var(--transition);
  font-size:14px;text-align:center;
  background:var(--surface);
  user-select:none;
}
.match-item:hover{border-color:var(--primary);transform:scale(1.02)}
.match-item.active{background:var(--primary-dim);border-color:var(--primary);color:var(--primary);font-weight:600}
.match-item.used{opacity:.4;pointer-events:none}
.match-item.paired{background:linear-gradient(135deg,var(--primary),var(--primary2));color:#fff;border-color:transparent}
.matching-pairs{
  display:flex;flex-wrap:wrap;gap:8px;
  justify-content:center;margin-top:16px;min-height:30px;
}
.match-pair{
  display:inline-flex;align-items:center;gap:6px;
  padding:4px 14px;
  background:var(--primary-dim);
  border-radius:20px;
  font-size:13px;font-weight:500;
  animation:fadeIn .2s ease;
}

/* Ordering */
.test-ordering{max-width:520px;margin:0 auto 24px}
.ordering-hint{font-size:13px;color:var(--text3);margin-bottom:12px}
.ordering-list{display:flex;flex-direction:column;gap:6px}
.order-item{
  display:flex;align-items:center;gap:12px;
  padding:12px 16px;
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius-sm);
  cursor:pointer;
  transition:all var(--transition);
  font-size:14px;user-select:none;
}
.order-item:hover{border-color:var(--primary);background:var(--primary-dim)}
.order-item.dragging{opacity:.4;border-style:dashed}
.order-item.drag-over{border-color:var(--primary2);border-style:dashed;background:var(--primary-dim)}
.order-item .order-handle{color:var(--text3);font-size:20px;cursor:grab;flex-shrink:0}
.order-item .order-idx{font-weight:700;color:var(--primary);min-width:24px;flex-shrink:0}

/* Short answer */
.test-short{max-width:500px;margin:0 auto 24px}
.short-input{
  width:100%;padding:14px 18px;
  border:1px solid var(--border);
  border-radius:var(--radius-sm);
  background:var(--surface);
  color:var(--text);
  font-size:15px;font-family:var(--font);
  resize:vertical;
  transition:border-color var(--transition),box-shadow var(--transition);
  outline:none;
}
.short-input:focus{
  border-color:var(--primary);
  box-shadow:0 0 0 4px var(--primary-glow);
}

/* Test nav & dots */
.test-nav{
  display:flex;gap:14px;
  justify-content:center;align-items:center;
  margin-top:12px;
}
.test-dots{display:flex;gap:5px;flex-wrap:wrap;max-width:260px}
.test-dot{
  width:10px;height:10px;
  border-radius:50%;
  background:var(--border);
  transition:all var(--transition);
  cursor:pointer;
}
.test-dot.active{background:var(--primary);transform:scale(1.4)}
.test-dot.answered{background:var(--success)}

/* Results */
.results-grid{
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:14px;max-width:560px;
  margin:28px auto;
}
.result-card{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:24px 12px;
  text-align:center;
  backdrop-filter:blur(10px);
  transition:all var(--transition);
}
.result-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-lg)}
.result-card.correct .result-num{color:var(--success)}
.result-card.wrong .result-num{color:var(--error)}
.result-num{font-size:32px;font-weight:800;margin-bottom:4px}
.result-label{font-size:12px;color:var(--text2);text-transform:uppercase;letter-spacing:.5px;font-weight:600}
.result-score{font-size:24px;font-weight:700;margin:20px 0}

/* Review */
#testReview{text-align:left;max-width:700px;margin:0 auto;padding:20px 0}
.review-item{border:1px solid var(--border);border-radius:var(--radius-sm);padding:16px 20px;margin-bottom:12px;background:var(--surface);transition:all var(--transition)}
.review-header{display:flex;align-items:center;gap:10px;margin-bottom:8px}
.review-num{font-weight:700;color:var(--primary);min-width:28px}
.review-type{font-size:11px;color:var(--text3);background:var(--primary-dim);padding:2px 10px;border-radius:10px;font-weight:500}
.review-status{font-size:18px;margin-left:auto;font-weight:700}
.review-item.correct .review-status{color:var(--success)}
.review-item.wrong .review-status{color:var(--error)}
.review-question{font-size:14px;margin-bottom:8px;line-height:1.5}
.review-answer{font-size:13px;padding:6px 12px;border-radius:6px;margin-bottom:4px;line-height:1.4}
.review-answer.wrong{background:rgba(239,68,68,.1);color:var(--error)}
.review-answer.correct{background:rgba(34,197,94,.1);color:var(--success)}

/* ===== Toast ===== */
.toast{
  position:fixed;bottom:28px;left:50%;
  transform:translateX(-50%) translateY(100px);
  background:var(--text);
  color:var(--bg);
  padding:12px 28px;
  border-radius:var(--radius-sm);
  font-size:14px;font-weight:500;
  z-index:200;white-space:nowrap;
  box-shadow:0 10px 40px rgba(0,0,0,.3);
  opacity:0;
  transition:all .5s cubic-bezier(.22,1,.36,1);
  pointer-events:none;
}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}

/* ===== Responsive ===== */
@media(max-width:768px){
  .hamburger{display:flex}
  .nav-center{
    display:none;
    position:absolute;top:var(--nav-h);left:0;right:0;
    background:var(--surface);
    flex-direction:column;padding:14px;
    border-bottom:1px solid var(--border);
    gap:4px;
    backdrop-filter:blur(20px);
  }
  .nav-center.open{display:flex}
  .nav-progress{display:none}
  .hero h1{font-size:26px}
  .hero-stats{gap:24px}
  .card-grid{grid-template-columns:1fr}
  .results-grid{grid-template-columns:repeat(2,1fr)}
  .matching-cols{grid-template-columns:1fr;gap:12px}
  .test-topbar{flex-wrap:wrap;gap:10px}
  .test-mid{flex:auto;width:100%}
}