/* ───────── RESET & VARIABLES ───────── */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}

:root{
  --bg:#09090b;
  --surface:rgba(24, 24, 27, 0.65);
  --surface2:rgba(39, 39, 42, 0.6);
  --border:rgba(255,255,255,0.08);
  --green:#10b981;
  --green-dim:#059669;
  --amber:#f59e0b;
  --red:#ef4444;
  --blue:#3b82f6;
  --text:#f8fafc;
  --muted:#94a3b8;
  --radius:16px;
  --shadow:0 12px 32px rgba(0,0,0,.45);
}
h1 {
  position: absolute;
  left: -9999px;
}

body{
  
  font-family:'Inter', sans-serif;
  background-color:var(--bg);
  background-image: 
    radial-gradient(circle at 15% 50%, rgba(59,220,140,0.06), transparent 30%),
    radial-gradient(circle at 85% 30%, rgba(91,154,245,0.06), transparent 30%);
  color:var(--text);
  min-height:100vh;
  overflow-x:hidden;
  scroll-behavior: smooth;
}

/* ───────── SCROLLBAR ───────── */
::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 6px;
  border: 2px solid var(--bg);
}
::-webkit-scrollbar-thumb:hover {
  background: var(--muted);
}

/* Subtle grid overlay */
@keyframes panGrid {
  0% { transform: translateY(0); }
  100% { transform: translateY(48px); }
}
body::before{
  content:'';
  position:fixed;inset:-48px 0 0 0;
  background-image:
    linear-gradient(rgba(59,220,140,.04) 1px,transparent 1px),
    linear-gradient(90deg,rgba(59,220,140,.04) 1px,transparent 1px);
  background-size:48px 48px;
  pointer-events:none;z-index:0;
  animation: panGrid 20s linear infinite;
  mask-image: radial-gradient(circle at center, black 40%, transparent 80%);
  -webkit-mask-image: radial-gradient(circle at center, black 40%, transparent 80%);
}

/* ───────── NAV ───────── */
nav{
  display:flex;align-items:center;justify-content:space-between;
  padding:18px 40px;
  background:rgba(14,17,23,.85);
  backdrop-filter:blur(12px);
  border-bottom:1px solid var(--border);
  position:sticky;top:0;z-index:100;
}
.logo{
  font-family:'Outfit', sans-serif;
  font-weight:800;font-size:1.4rem;
  color:var(--green);
  letter-spacing:-0.5px;
}
.logo span{color:var(--text)}
.nav-tabs{display:flex;gap:4px}
.nav-tab{
  font-family:'Inter', sans-serif;
  font-size:.85rem;font-weight:500;
  padding:7px 16px;
  border:1px solid transparent;
  border-radius:8px;
  cursor:pointer;
  color:var(--muted);
  background:none;
  transition:all .2s;
}
.nav-tab:hover{color:var(--text);border-color:var(--border)}
.nav-tab.active{
  color:var(--green);
  background:rgba(59,220,140,.08);
  border-color:rgba(59,220,140,.2);
}

/* ───────── MAIN LAYOUT ───────── */
main{
  max-width:860px;
  margin:0 auto;
  padding:40px 24px 80px;
  position:relative;z-index:1;
  transition: max-width 0.4s cubic-bezier(0.16, 1, 0.3, 1), width 0.4s;
}
main.wide {
  max-width: 98% !important;
  width: 98% !important;
}

/* ───────── SECTION PAGES ───────── */
.page{display:none}
.page.active{display:block}

/* ───────── HERO ───────── */
.hero{
  text-align:center;
  padding:48px 0 56px;
}
@keyframes pulseGlow{
  0%{box-shadow:0 0 0 0 rgba(59,220,140,.4)}
  70%{box-shadow:0 0 0 8px rgba(59,220,140,0)}
  100%{box-shadow:0 0 0 0 rgba(59,220,140,0)}
}
.hero-badge{
  display:inline-flex;align-items:center;gap:6px;
  font-size:.75rem;font-weight:500;
  color:var(--green);
  background:rgba(59,220,140,.08);
  border:1px solid rgba(59,220,140,.2);
  border-radius:999px;
  padding:5px 14px;
  margin-bottom:24px;
  animation:pulseGlow 2s infinite;
}
.hero h1{
  font-family:'Outfit', sans-serif;
  font-size:clamp(2.5rem,5vw,3.8rem);
  font-weight:800;
  letter-spacing: -1px;
  line-height:1.1;
  margin-bottom:16px;
}
.hero h1 em{
  font-style:normal;
  background:linear-gradient(90deg,var(--green),#5be8c0);
  -webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;
}
.hero p{
  font-size:1rem;color:var(--muted);
  max-width:480px;margin:0 auto 36px;
  line-height:1.7;
}

.card{
  background:var(--surface);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:28px;
  margin-bottom:20px;
  transition:all .3s ease;
  box-shadow: 0 4px 14px rgba(0,0,0,0.1);
}
.card:hover{
  border-color:rgba(59,220,140,.3);
  box-shadow: 0 8px 24px rgba(59,220,140,.08);
  transform: translateY(-2px);
} 
.card-title{
  font-family:'Outfit', sans-serif;
  font-size:1.15rem;font-weight:700;
  margin-bottom:18px;
  display:flex;align-items:center;gap:8px;
  letter-spacing:-0.3px;
}
.card-title .icon{font-size:1.1rem}

/* ───────── UPLOAD ZONE ───────── */
.upload-zone{
  border:2px dashed var(--border);
  border-radius:var(--radius);
  padding:40px 24px;
  text-align:center;
  cursor:pointer;
  transition:all .3s cubic-bezier(0.4, 0, 0.2, 1);
  position:relative;
  background: linear-gradient(145deg, rgba(29,37,53,0.4) 0%, rgba(22,27,39,0.4) 100%);
  backdrop-filter: blur(8px);
}
.upload-zone:hover,.upload-zone.dragover{
  border-color:var(--green);
  background:rgba(59,220,140,.06);
  transform: scale(1.02);
  box-shadow: 0 0 20px rgba(59,220,140,.12);
}
.upload-zone input[type=file]{
  position:absolute;inset:0;opacity:0;cursor:pointer;
}
.upload-icon{font-size:2.4rem;margin-bottom:10px}
.upload-text{font-size:.9rem;color:var(--muted)}
.upload-text strong{color:var(--green)}

/* ───────── PROGRESS BAR ───────── */
.upload-progress{
  width:100%;height:4px;
  background:var(--border);
  border-radius:999px;
  margin-top:16px;
  overflow:hidden;
  display:none;
}
.upload-progress-bar{
  height:100%;
  background:linear-gradient(90deg,var(--green),#5be8c0);
  border-radius:999px;
  width:0%;
  transition:width .3s ease;
}

/* ───────── BUTTONS ───────── */
.btn{
  font-family:'Outfit', sans-serif;
  font-size:.95rem;font-weight:600;
  padding:12px 20px;
  border:none;border-radius:10px;
  cursor:pointer;
  transition:all .2s ease;
  display:inline-flex;align-items:center;gap:7px;
}
.btn-primary{
  background:linear-gradient(135deg, var(--green), #059669); color:#fff;
  box-shadow: 0 4px 16px rgba(16, 185, 129, 0.25);
}
.btn-primary:hover{
  transform:translateY(-2px);
  box-shadow: 0 8px 24px rgba(16, 185, 129, 0.4);
  filter: brightness(1.1);
}
.btn-secondary{
  background:var(--surface2);color:var(--text);
  border:1px solid var(--border);
}
.btn-secondary:hover{border-color:var(--muted)}
.btn-outline{
  background:transparent;color:var(--green);
  border:1px solid rgba(59,220,140,.35);
}
.btn-outline:hover{background:rgba(59,220,140,.08)}
.btn:active{transform:scale(.97)}
.btn:disabled{opacity:.45;cursor:not-allowed;transform:none!important}
.btn-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:16px}

/* ───────── TOPIC CHIPS ───────── */
.topics-grid{
  display:flex;flex-wrap:wrap;gap:10px;
  margin-top:8px;
}
.topic-chip{
  font-size:.82rem;font-weight:500;
  padding:8px 16px;
  border:1px solid var(--border);
  border-radius:999px;
  background:var(--surface2);
  cursor:pointer;
  transition:all .18s;
  display:flex;align-items:center;gap:6px;
}
.topic-chip:hover{
  border-color:var(--green);
  color:var(--green);
  background:rgba(59,220,140,.06);
}

/* ───────── KNOWLEDGE CHECK MODAL ───────── */
.know-modal{
  position:fixed;inset:0;z-index:200;
  display:none;align-items:center;justify-content:center;
  background:rgba(0,0,0,.6);
  backdrop-filter:blur(4px);
}
.know-modal.show{display:flex}
.know-card{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:20px;
  padding:36px;
  max-width:420px;width:90%;
  text-align:center;
  animation:pop .25s ease;
}
@keyframes pop{from{transform:scale(.9);opacity:0}to{transform:scale(1);opacity:1}}
.know-card h3{
  font-family:'Syne',sans-serif;
  font-size:1.25rem;margin-bottom:10px;
}
.know-card p{font-size:.9rem;color:var(--muted);margin-bottom:24px;line-height:1.6}
.know-btns{display:flex;gap:12px;justify-content:center}

/* ───────── QUIZ ───────── */
#quizPage{display:none}
.quiz-header{
  display:flex;align-items:center;justify-content:space-between;
  margin-bottom:24px;flex-wrap:wrap;gap:12px;
}
.quiz-meta{font-size:.82rem;color:var(--muted)}
.quiz-meta strong{color:var(--text)}

/* Progress bar */
.progress-track{
  width:100%;height:6px;
  background:var(--border);
  border-radius:999px;
  margin-bottom:24px;overflow:hidden;
}
.progress-fill{
  height:100%;
  background:linear-gradient(90deg,var(--green),#5be8c0);
  border-radius:999px;
  transition:width .4s ease;
}

/* Timer */
.timer-ring{
  width:52px;height:52px;
  position:relative;flex-shrink:0;
}
.timer-ring svg{transform:rotate(-90deg)}
.timer-ring circle{fill:none;stroke-width:4}
.timer-bg{stroke:var(--border)}
.timer-arc{
  stroke:var(--green);
  stroke-linecap:round;
  transition:stroke-dashoffset .9s linear,stroke .3s;
}
.timer-label{
  position:absolute;inset:0;
  display:flex;align-items:center;justify-content:center;
  font-family:'Syne',sans-serif;
  font-size:.85rem;font-weight:700;
}

/* Question card */
.question-card{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:28px;
  margin-bottom:16px;
}
.question-number{
  font-size:.75rem;font-weight:600;
  color:var(--green);letter-spacing:.5px;
  text-transform:uppercase;margin-bottom:10px;
}
.question-text{
  font-family:'Syne',sans-serif;
  font-size:1.05rem;font-weight:600;
  line-height:1.5;
}

/* Options */
.options-list{display:flex;flex-direction:column;gap:10px;margin-top:4px}
.option{
  display:flex;align-items:center;gap:14px;
  padding:14px 18px;
  border:1px solid var(--border);
  border-radius:11px;
  cursor:pointer;
  transition:all .18s;
  user-select:none;
}
.option:hover{border-color:var(--green);background:rgba(59,220,140,.04)}
.option.selected{
  border-color:var(--green);
  background:rgba(59,220,140,.1);
}
.option.correct{border-color:var(--green);background:rgba(59,220,140,.15)}
.option.wrong{border-color:var(--red);background:rgba(242,92,92,.12)}
.option input[type=radio]{display:none}
.opt-letter{
  width:30px;height:30px;flex-shrink:0;
  display:flex;align-items:center;justify-content:center;
  border-radius:7px;border:1px solid var(--border);
  font-size:.8rem;font-weight:600;color:var(--muted);
  transition:all .18s;background:var(--surface2);
}
.option.selected .opt-letter{
  background:var(--green);color:#0e1117;border-color:var(--green);
}
.opt-text{font-size:.92rem;line-height:1.4}

/* ───────── SCORE SCREEN ───────── */
.score-screen{text-align:center;padding:20px 0}
.score-circle{
  width:130px;height:130px;
  border-radius:50%;
  border:4px solid var(--green);
  display:flex;flex-direction:column;
  align-items:center;justify-content:center;
  margin:0 auto 24px;
  background:rgba(59,220,140,.07);
}
.score-num{
  font-family:'Syne',sans-serif;
  font-size:2.2rem;font-weight:800;color:var(--green);
}
.score-denom{font-size:.8rem;color:var(--muted)}
.score-msg{
  font-family:'Syne',sans-serif;
  font-size:1.3rem;font-weight:700;margin-bottom:6px;
}
.score-pct{font-size:.9rem;color:var(--muted);margin-bottom:28px}

/* Weak topics */
.weak-list{
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:20px;
  text-align:left;
  margin-bottom:20px;
}
.weak-list h4{
  font-size:.8rem;font-weight:600;
  color:var(--amber);letter-spacing:.4px;
  text-transform:uppercase;margin-bottom:12px;
}
.weak-item{
  display:flex;align-items:flex-start;gap:10px;
  padding:10px 0;
  border-bottom:1px solid var(--border);
  font-size:.88rem;
  line-height:1.5;
}
.weak-item:last-child{border-bottom:none;padding-bottom:0}
.weak-item::before{content:'✗';color:var(--red);font-weight:700;flex-shrink:0;margin-top:1px}

/* ───────── AI TUTOR ───────── */
.tutor-input-row{
  display:flex;gap:10px;
  align-items:flex-start;
}
.tutor-input{
  flex:1;
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:10px;
  color:var(--text);
  font-family:'DM Sans',sans-serif;
  font-size:.9rem;
  padding:12px 16px;
  resize:vertical;min-height:56px;
  transition:border-color .2s;
  outline:none;
}
.tutor-input:focus{border-color:var(--green)}
.tutor-answer{
  margin-top:20px;
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:20px 24px;
  font-size:.92rem;
  line-height:1.75;
  display:none;
}
.tutor-answer h1, .tutor-answer h2, .tutor-answer h3,
.explanation-panel h1, .explanation-panel h2, .explanation-panel h3 {
  font-family:'Syne',sans-serif;margin-bottom:10px;margin-top:16px;
}
.tutor-answer code, .explanation-panel code {
  background:rgba(59,220,140,.12);
  padding:2px 6px;border-radius:5px;
  font-size:.85rem;color:var(--green);
  font-family: monospace;
}
.tutor-answer pre, .explanation-panel pre {
  background:var(--bg);
  padding:16px;border-radius:10px;
  border:1px solid var(--border);
  overflow-x:auto;margin:12px 0;
}
.tutor-answer ul, .tutor-answer ol, .explanation-panel ul, .explanation-panel ol {
  padding-left:22px;margin:8px 0;
}
.tutor-answer li, .explanation-panel li {
  margin-bottom:6px;
}

.thinking{
  display:none;
  align-items:center;gap:10px;
  padding:14px 18px;
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:var(--radius);
  margin-top:20px;
  font-size:.88rem;color:var(--muted);
}
.thinking.show{display:flex}
.dot-anim{display:flex;gap:5px}
.dot-anim span{
  width:7px;height:7px;border-radius:50%;
  background:var(--green);
  animation:bounce 1.1s infinite;
}
.dot-anim span:nth-child(2){animation-delay:.18s}
.dot-anim span:nth-child(3){animation-delay:.36s}
@keyframes bounce{0%,80%,100%{transform:scale(.6)}40%{transform:scale(1)}}

/* ───────── DASHBOARD ───────── */
.stats-grid{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(160px,1fr));
  gap:14px;
  margin-bottom:20px;
}
.stat-card{
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:20px;
  text-align:center;
}
.stat-val{
  font-family:'Syne',sans-serif;
  font-size:1.8rem;font-weight:800;color:var(--green);
}
.stat-lbl{font-size:.78rem;color:var(--muted);margin-top:4px}

.revision-plan{
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:20px;
}
.revision-plan h4{
  font-family:'Syne',sans-serif;
  font-size:.95rem;font-weight:700;margin-bottom:14px;
}
.revision-item{
  display:flex;align-items:center;gap:12px;
  padding:10px 0;
  border-bottom:1px solid var(--border);
  font-size:.88rem;
}
.revision-item:last-child{border-bottom:none}
.rev-icon{font-size:1.1rem}

/* ───────── TOAST ───────── */
.toast{
  position:fixed;bottom:28px;right:28px;
  background:var(--surface2);
  border:1px solid var(--border);
  border-radius:11px;
  padding:13px 20px;
  font-size:.85rem;
  box-shadow:var(--shadow);
  z-index:999;
  opacity:0;transform:translateY(12px);
  transition:all .3s;
  pointer-events:none;
}
.toast.show{opacity:1;transform:translateY(0)}

/* ───────── DARK MODE TOGGLE ───────── */
.dark-toggle{
  background:none;border:1px solid var(--border);
  border-radius:8px;padding:6px 10px;
  color:var(--muted);cursor:pointer;font-size:1rem;
  transition:all .2s;
}
.dark-toggle:hover{color:var(--text);border-color:var(--muted)}

/* ───────── MISC ───────── */
.separator{
  height:1px;background:var(--border);margin:24px 0;
}
.empty-state{
  text-align:center;padding:50px 24px;
  color:var(--muted);font-size:.95rem;
  background:var(--surface2);
  border-radius:var(--radius);
  border:1px dashed var(--border);
}
.empty-state .empty-icon{font-size:2.8rem;margin-bottom:14px; opacity:0.8;}

.difficulty-row{
  display:flex;gap:8px;flex-wrap:wrap;margin-top:12px;
}
.diff-btn{
  font-size:.78rem;font-weight:600;
  padding:6px 14px;border-radius:999px;
  border:1px solid var(--border);
  background:none;color:var(--muted);
  cursor:pointer;transition:all .18s;
}
.diff-btn:hover,.diff-btn.active{
  background:var(--surface2);color:var(--text);border-color:var(--muted);
}
.diff-btn.active[data-d=easy]{border-color:#3bdc8c;color:#3bdc8c}
.diff-btn.active[data-d=medium]{border-color:var(--amber);color:var(--amber)}
.diff-btn.active[data-d=hard]{border-color:var(--red);color:var(--red)}

/* Explanation panel */
.explanation-panel{
  background:var(--surface2);
  border-left:3px solid var(--green);
  border-radius:0 var(--radius) var(--radius) 0;
  padding:20px 24px;
  font-size:.92rem;line-height:1.75;
  display:none;margin-top:16px;
}
.explanation-panel.show{display:block}

/* Scroll fade-in */
@keyframes fadeUp{from{opacity:0;transform:translateY(16px)}to{opacity:1;transform:translateY(0)}}
.card,.question-card,.stat-card{animation:fadeUp .35s ease both}

/* ───────── RESPONSIVE ───────── */
@media(max-width:800px){
  nav{flex-wrap:wrap; justify-content:center; gap:12px; padding:14px 18px}
  .nav-tabs{flex-wrap:wrap; justify-content:center; width:100%; order:3}
  main{padding:24px 14px 60px}
  .tutor-input-row{flex-direction:column}
  .know-btns{flex-direction:column}
}
@media(max-width:400px){
  .nav-tab{padding:6px 10px; font-size:0.75rem}
}
/* ───────── MIND MAP VISIBILITY ───────── */
#mindmapContainer {
  overflow: auto;
  min-height: 40vh; /* Allow it to be smaller but not completely collapsed */
  height: fit-content;
  max-height: 85vh;
  width: 100%;
  background: var(--surface2);
  border-radius: 12px;
  border: 1px solid var(--border);
  position: relative;
  cursor: grab;
  box-shadow: inset 0 0 20px rgba(0,0,0,0.2);
}
#mindmapContainer:active {
  cursor: grabbing;
}
.mermaid {
  min-width: 100%;
  display: block;
  text-align: center;
  padding: 40px;
}
.mermaid svg {
  width: max-content !important; /* Respect the natural width calculated by Mermaid */
  max-width: none !important;
  height: auto !important;
}

/* ───────── MOBILE RESPONSIVENESS ───────── */
@media (max-width: 768px) {
  nav { flex-direction: column; padding: 12px 16px; gap: 14px; position:relative; }
  .logo { justify-content:center; }
  .nav-tabs { width: 100%; overflow-x: auto; white-space: nowrap; -webkit-overflow-scrolling: touch; padding-bottom: 6px; }
  .nav-tab { font-size: 0.82rem; padding: 6px 12px; }
  .nav-tabs::-webkit-scrollbar { height: 4px; }
  .nav-tabs::-webkit-scrollbar-thumb { background: var(--green); border-radius: 4px; }
  main { padding: 24px 16px 60px; max-width: 100vw; }
  .hero h1 { font-size: 2.2rem; }
  .hero { padding: 24px 0 36px; }
  .card { padding: 16px; }
  .card-title { font-size: 1rem; }
  .btn { width: 100%; justify-content: center; }
  .top-right-nav { position:absolute; right:16px; top:12px; }
}

/* ───────── FLASHCARDS ───────── */
.flashcard-container {
  perspective: 1200px;
  width: 100%;
  max-width: 440px;
  height: 280px;
  margin: 0 auto 32px;
}

.flashcard {
  position: relative;
  width: 100%;
  height: 100%;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 20px 40px rgba(0,0,0,0.3);
  border-radius: 24px;
}

.flashcard.flipped {
  transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px;
  text-align: center;
  border-radius: 24px;
  border: 1px solid var(--border);
  background: linear-gradient(135deg, var(--surface2) 0%, rgba(20,20,25,0.9) 100%);
}

.flashcard-back {
  transform: rotateY(180deg);
  background: linear-gradient(135deg, rgba(20,20,25,0.9) 0%, var(--surface2) 100%);
}

.card-label {
  position: absolute;
  top: 20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 2px;
  color: var(--green);
  opacity: 0.8;
}

.card-content {
  font-family: 'Outfit', sans-serif;
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.4;
  color: var(--text);
}

.card-hint {
  position: absolute;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.72rem;
  color: var(--muted);
  font-style: italic;
}

.deck-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  user-select: none;
}

.card-counter {
  font-family: 'Syne', sans-serif;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--muted);
}

#currentCardNum {
  color: var(--green);
  font-size: 1.4rem;
}

@media(max-width: 500px) {
  .flashcard-container {
    height: 320px;
  }
  .card-content {
    font-size: 1.1rem;
  }
}