/* ═══════════════════════════════════════════════════
   ETOPIK FLASHCARD — OCEAN BLUE KOREAN UI
   Duolingo meets K-education aesthetic
   ═══════════════════════════════════════════════════ */

@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+KR:wght@400;600;800;900&display=swap');

:root{
  --bg: #F4F8FB;
  --panel: #FFFFFF;
  --accent: #3B82F6;
  --accent-light: #60A5FA;
  --accent-dark: #2563EB;
  --accent-glow: rgba(59,130,246,0.12);
  --sky: #7DD3FC;
  --sky-light: #E0F2FE;
  --rose: #FB7185;
  --rose-light: #FFE4E8;
  --mint: #34D399;
  --mint-light: #D1FAE5;
  --amber: #FBBF24;
  --amber-light: #FEF3C7;
  --cream: #FEFCF6;
  --text: #1E293B;
  --text-soft: #64748B;
  --text-muted: #94A3B8;
  --border: rgba(59,130,246,0.1);
  --shadow-soft: 0 2px 12px rgba(30,41,59,0.05);
  --shadow-card: 0 10px 36px rgba(59,130,246,0.1);
  --shadow-float: 0 8px 28px rgba(59,130,246,0.15);
  --radius: 18px;
  --radius-sm: 13px;
  --radius-xs: 10px;
}

*{ box-sizing:border-box; }

body{
  font-family: "Noto Sans KR", -apple-system, sans-serif !important;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

/* Subtle gradient background */
#flash-app::before{
  content:''; position:fixed; inset:0;
  background:
    radial-gradient(ellipse at 15% 0%, rgba(125,211,252,0.12) 0%, transparent 50%),
    radial-gradient(ellipse at 85% 90%, rgba(59,130,246,0.06) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 40%, rgba(52,211,153,0.04) 0%, transparent 50%);
  pointer-events:none; z-index:-1;
}

#flash-app{ max-width:1280px; margin:0 auto; padding:20px 18px; position:relative; }
.wrap{ display:grid; grid-template-columns:300px 1fr; gap:24px; align-items:start; }

/* ═══════ LEFT PANEL ═══════ */
.left-panel{
  position:sticky; top:20px;
  background:rgba(255,255,255,0.75);
  backdrop-filter:blur(16px); -webkit-backdrop-filter:blur(16px);
  border-radius:var(--radius); border:1px solid var(--border);
  padding:20px 16px; box-shadow:var(--shadow-soft);
}
.left-header{ display:flex; justify-content:space-between; align-items:center; margin-bottom:16px; }
.left-title{
  font-size:18px; font-weight:800;
  background:linear-gradient(135deg, var(--accent), var(--sky));
  -webkit-background-clip:text; -webkit-text-fill-color:transparent; background-clip:text;
}
.deck-toggle-btn{
  display:none; background:var(--accent); color:#fff; border:none;
  padding:10px 16px; border-radius:var(--radius-xs); cursor:pointer;
  font-weight:700; font-size:14px; transition:all .2s;
}
.deck-toggle-btn:active{ transform:scale(0.96); }
#deck-list{ display:grid; grid-template-columns:1fr 1fr; gap:8px; }

/* ═══════ DECK BUTTONS ═══════ */
.deck-btn{
  background:var(--cream); border:1.5px solid rgba(59,130,246,0.08);
  padding:14px 10px 12px; border-radius:var(--radius-sm);
  text-align:center; font-weight:600; cursor:pointer;
  transition:all .2s cubic-bezier(.4,0,.2,1);
  box-shadow:var(--shadow-soft); position:relative; overflow:hidden;
}
.deck-btn:hover{ transform:translateY(-2px); box-shadow:var(--shadow-float); border-color:var(--sky); }
.deck-btn:active{ transform:translateY(0) scale(0.98); }
.deck-btn.active{
  background:linear-gradient(135deg, var(--accent), var(--accent-light));
  color:#fff; border-color:transparent;
  box-shadow:var(--shadow-float), 0 0 0 3px var(--accent-glow);
}
.deck-btn.active .meta{ color:rgba(255,255,255,0.8); opacity:1; }
.deck-btn > div{ font-size:13px; font-weight:700; position:relative; z-index:1; }
.deck-btn .meta{
  display:block; margin-top:5px; font-size:10.5px;
  color:var(--text-muted); font-weight:500; position:relative; z-index:1;
}

/* Deck animation */
.deck-btn{ animation:deck-fade 0.3s ease both; }
.deck-btn:nth-child(1){animation-delay:0s;} .deck-btn:nth-child(2){animation-delay:.03s;}
.deck-btn:nth-child(3){animation-delay:.06s;} .deck-btn:nth-child(4){animation-delay:.09s;}
.deck-btn:nth-child(5){animation-delay:.12s;} .deck-btn:nth-child(6){animation-delay:.15s;}
@keyframes deck-fade{ from{opacity:0;transform:translateY(8px);} to{opacity:1;transform:translateY(0);} }

/* ═══════ CONTROLS ═══════ */
.controls-top{
  display:flex; justify-content:space-between; align-items:center;
  margin-bottom:14px; gap:10px; flex-wrap:wrap;
}
.btn{
  background:rgba(255,255,255,0.85); backdrop-filter:blur(10px);
  border:1.5px solid var(--border); padding:10px 16px;
  border-radius:var(--radius-xs); cursor:pointer; font-weight:700;
  font-size:13px; color:var(--text); transition:all .2s;
}
.btn:hover{ border-color:var(--sky); box-shadow:var(--shadow-soft); }
.btn:active{ transform:scale(0.97); }

#review-unknown-btn{
  background:linear-gradient(135deg, var(--accent), var(--accent-light));
  color:#fff; border:none;
  box-shadow:0 4px 16px rgba(59,130,246,0.25); font-size:13px;
}
#review-unknown-btn:hover{ box-shadow:0 6px 24px rgba(59,130,246,0.35); transform:translateY(-1px); }

/* ═══════ LEVEL TABS ═══════ */
.level-tabs{
  display:flex; gap:8px; margin-bottom:14px;
}
.level-tab{
  flex:1; padding:10px 16px; border-radius:var(--radius-xs);
  background:rgba(255,255,255,0.85); backdrop-filter:blur(10px);
  border:1.5px solid var(--border); cursor:pointer;
  font-weight:700; font-size:13px; color:var(--text);
  transition:all .2s; text-align:center;
}
.level-tab:hover{ border-color:var(--sky); box-shadow:var(--shadow-soft); }
.level-tab:active{ transform:scale(0.97); }
.level-tab.active{
  background:linear-gradient(135deg, var(--accent), var(--accent-light));
  color:#fff; border-color:transparent;
  box-shadow:0 4px 14px rgba(59,130,246,0.25);
}

/* ═══════ FLASHCARD ═══════ */
.card-wrapper{ perspective:1200px; background:transparent !important; }
.flashcard{
  width:100%; min-height:400px; border-radius:22px;
  position:relative; transform-style:preserve-3d;
  transition:transform .65s cubic-bezier(.23,1,.32,1);
  cursor:pointer; box-shadow:var(--shadow-card);
  animation:card-float 0.45s cubic-bezier(.23,1,.32,1);
}
@keyframes card-float{ from{opacity:0;transform:translateY(14px);} to{opacity:1;transform:translateY(0);} }
.flashcard.is-flipped{ transform:rotateY(180deg); }

.fc-face{
  position:absolute; inset:0; color:white; padding:28px;
  backface-visibility:hidden; -webkit-backface-visibility:hidden;
  border-radius:22px; text-align:center; overflow:hidden;
}

/* Front: deep blue gradient */
.fc-front{
  background:linear-gradient(150deg, #1E3A5F 0%, #172554 45%, #0F172A 100%);
}
.fc-front::before{
  content:''; position:absolute; top:-40%; right:-25%; width:70%; height:110%;
  background:radial-gradient(ellipse, rgba(59,130,246,0.2) 0%, transparent 60%);
  pointer-events:none;
}
.fc-front::after{
  content:''; position:absolute; bottom:-35%; left:-15%; width:55%; height:75%;
  background:radial-gradient(ellipse, rgba(125,211,252,0.1) 0%, transparent 60%);
  pointer-events:none;
}

/* Back: teal gradient */
.fc-back{
  background:linear-gradient(150deg, #134E4A 0%, #0F3D38 45%, #042F2E 100%);
  transform:rotateY(180deg);
}
.fc-back::before{
  content:''; position:absolute; top:-35%; left:-15%; width:60%; height:90%;
  background:radial-gradient(ellipse, rgba(52,211,153,0.12) 0%, transparent 60%);
  pointer-events:none;
}

.term{
  position:absolute; top:50%; left:50%; transform:translate(-50%,-50%);
  width:88%; text-align:center;
  font-family:"Noto Sans KR",sans-serif !important; font-weight:900;
  font-size:44px; line-height:1.3; word-break:keep-all;
  text-shadow:0 3px 16px rgba(0,0,0,.25); letter-spacing:-0.5px;
}
.meaning{ font-size:32px; font-weight:800; padding:0 16px; }

#flash-app .meaning{ color:#fff; }
#flash-app .fc-face{ color:#fff; }
.fc-back .meaning,.fc-back .reading,.fc-back > div{
  position:absolute !important; top:50% !important; left:50% !important;
  transform:translate(-50%,-50%) !important; width:88% !important;
  text-align:center !important; margin:0 !important; padding:0 !important;
}
.reading{ font-size:18px; opacity:.85; margin-bottom:10px; }

/* Card floating buttons — frosted glass */
.shuffle-icon{
  position:absolute; right:14px; top:14px; width:42px; height:42px;
  background:rgba(255,255,255,0.12); backdrop-filter:blur(10px);
  border-radius:11px; display:flex; align-items:center; justify-content:center;
  cursor:pointer; z-index:3; transition:all .2s; border:1px solid rgba(255,255,255,0.1);
}
.shuffle-icon:hover{ background:rgba(255,255,255,0.22); transform:rotate(15deg); }

.audio-in-card{
  position:absolute; left:50%; transform:translateX(-50%); bottom:20px;
  width:58px; height:58px; background:rgba(255,255,255,0.12);
  backdrop-filter:blur(10px); border-radius:50%;
  display:flex; align-items:center; justify-content:center;
  cursor:pointer; z-index:9999; transition:all .25s;
  border:1.5px solid rgba(255,255,255,0.12);
}
.audio-in-card:hover{
  background:rgba(255,255,255,0.28);
  transform:translateX(-50%) scale(1.07);
  box-shadow:0 0 20px rgba(255,255,255,0.12);
}

.next-circle{
  position:absolute; right:14px; bottom:14px; width:46px; height:46px;
  border-radius:50%; background:rgba(255,255,255,0.12); backdrop-filter:blur(10px);
  display:flex; align-items:center; justify-content:center;
  cursor:pointer; z-index:3; transition:all .2s; border:1px solid rgba(255,255,255,0.1);
}
.next-circle:hover{ background:rgba(255,255,255,0.25); transform:scale(1.05); }

/* ═══════ FLIP HINT ═══════ */
.flip-hint{
  width:100%; text-align:center; margin-top:10px; margin-bottom:2px;
  font-size:12px; font-weight:500; color:var(--text-muted); user-select:none;
}

/* ═══════ NAV BUTTONS ═══════ */
.nav-bottom{ display:flex; gap:12px; margin-top:16px; }
.nav-big{
  flex:1; padding:14px; font-weight:700; font-size:16px;
  border-radius:var(--radius-sm); cursor:pointer; border:none; transition:all .2s;
}
.nav-big:active{ transform:scale(0.97); }
.nav-prev{
  background:rgba(255,255,255,0.85); backdrop-filter:blur(8px);
  color:var(--accent); border:1.5px solid var(--border);
}
.nav-prev:hover{ border-color:var(--sky); }
.nav-next{
  background:linear-gradient(135deg, var(--accent), var(--accent-light));
  color:#fff; box-shadow:0 4px 16px rgba(59,130,246,0.25);
}
.nav-next:hover{ box-shadow:0 6px 20px rgba(59,130,246,0.35); transform:translateY(-1px); }

/* ═══════ SRS BUTTONS ═══════ */
.srs-row{ margin-top:14px; display:flex; gap:10px; position:relative; }
.srs{
  flex:1; text-align:center; display:flex; flex-direction:column;
  align-items:center; gap:1px; padding:14px 8px;
  border-radius:var(--radius-sm); border:1.5px solid transparent;
  cursor:pointer; font-weight:600;
  transition:all .18s cubic-bezier(.4,0,.2,1);
  animation:srs-appear 0.3s cubic-bezier(.23,1,.32,1) both;
}
.srs:nth-child(1){animation-delay:.05s;} .srs:nth-child(2){animation-delay:.1s;} .srs:nth-child(3){animation-delay:.15s;}
@keyframes srs-appear{ from{opacity:0;transform:scale(0.92) translateY(6px);} to{opacity:1;transform:scale(1) translateY(0);} }
.srs:active{ transform:scale(0.95); }
.srs-label{ font-size:14px; }

.hard{ background:var(--rose-light); color:#BE123C; border-color:rgba(251,113,133,0.15); }
.hard:hover{ border-color:var(--rose); box-shadow:0 4px 14px rgba(251,113,133,0.15); transform:translateY(-1px); }
.normal{ background:var(--sky-light); color:#0369A1; border-color:rgba(125,211,252,0.2); }
.normal:hover{ border-color:var(--sky); box-shadow:0 4px 14px rgba(125,211,252,0.2); transform:translateY(-1px); }
.easy{ background:var(--mint-light); color:#047857; border-color:rgba(52,211,153,0.15); }
.easy:hover{ border-color:var(--mint); box-shadow:0 4px 14px rgba(52,211,153,0.15); transform:translateY(-1px); }

/* ═══════ TIP + "CÁCH HỌC?" BUTTON ═══════ */
.tip{
  text-align:center; margin-top:8px; color:var(--text-muted);
  font-size:12px; font-weight:500; line-height:1.6;
}
.srs-how-btn{
  background:none; border:none; color:var(--accent);
  font-weight:700; font-size:12px; cursor:pointer;
  padding:2px 8px; border-radius:6px;
  transition:all .15s;
  text-decoration:underline;
  text-decoration-color:rgba(59,130,246,0.3);
  text-underline-offset:2px;
}
.srs-how-btn:hover{
  background:var(--sky-light); color:var(--accent-dark);
  text-decoration-color:var(--accent);
}

/* ═══════ EXAMPLE PANEL ═══════ */
.example-panel{
  margin-top:14px; background:rgba(255,255,255,0.65);
  backdrop-filter:blur(10px); border-radius:var(--radius-sm);
  padding:16px 18px; border:1px solid var(--border);
  display:flex; align-items:flex-start; gap:12px;
}
.example-panel-text{ flex:1; min-width:0; }
#example-kr{ font-size:15px; font-weight:700; color:var(--text); line-height:1.6; margin-bottom:6px; }
#example-vi{
  font-size:13px; color:var(--text-soft); line-height:1.5;
  font-style:italic; border-left:3px solid var(--sky); padding-left:12px;
}
#example-audio{
  width:48px; height:48px; min-width:48px; min-height:48px;
  flex-shrink:0; align-self:center;
  border-radius:50%; background:#fff;
  color:var(--accent); border:2px solid var(--accent);
  cursor:pointer; display:flex;
  align-items:center; justify-content:center; font-size:22px;
  box-shadow:0 3px 12px rgba(59,130,246,0.15); transition:all .2s;
  -webkit-tap-highlight-color:transparent;
}
#example-audio:hover{ background:var(--accent); color:#fff; transform:scale(1.05); box-shadow:0 5px 18px rgba(59,130,246,0.3); }

/* ═══════ SRS INFO POPUP ═══════ */
.srs-popup-overlay{
  position:fixed; inset:0; background:rgba(15,23,42,0.4);
  backdrop-filter:blur(3px); z-index:99998; animation:srs-fade-in .2s ease;
}
@keyframes srs-fade-in{ from{opacity:0;} to{opacity:1;} }
.srs-popup-box{
  position:fixed; bottom:0; left:0; right:0; max-width:480px; margin:0 auto;
  background:#fff; border-radius:22px 22px 0 0; padding:26px 22px 34px;
  z-index:99999; box-shadow:0 -10px 44px rgba(15,23,42,0.12);
  animation:srs-popup-slide 0.3s cubic-bezier(.23,1,.32,1);
  max-height:85vh; overflow-y:auto;
}
@keyframes srs-popup-slide{ from{transform:translateY(100%);} to{transform:translateY(0);} }
.srs-popup-close{
  position:absolute; top:14px; right:16px; background:var(--sky-light);
  border:none; font-size:14px; color:var(--accent); cursor:pointer;
  padding:6px 10px; border-radius:8px; transition:all .15s;
}
.srs-popup-close:hover{ background:var(--accent); color:#fff; }
.srs-popup-box h3{ margin:0 0 8px; font-size:17px; font-weight:800; color:var(--text); }
.srs-popup-box p{ font-size:13.5px; color:var(--text-soft); line-height:1.65; margin:0 0 16px; }
.srs-info-row{
  display:flex; gap:14px; align-items:flex-start; margin-bottom:14px;
  padding:12px; border-radius:12px; background:#F8FAFC;
}
.srs-info-dot{
  width:32px; height:32px; border-radius:10px; flex-shrink:0;
  display:flex; align-items:center; justify-content:center; font-size:16px;
}
.srs-info-dot.hard{ background:var(--rose-light); }
.srs-info-dot.normal{ background:var(--sky-light); }
.srs-info-dot.easy{ background:var(--mint-light); }
.srs-info-row b{ font-size:14px; display:block; margin-bottom:3px; color:var(--text); }
.srs-info-row span{ font-size:12.5px; color:var(--text-soft); line-height:1.55; }
.srs-info-tip{
  background:linear-gradient(135deg, var(--sky-light), var(--amber-light));
  border-radius:12px; padding:12px 16px; font-size:13px !important;
  color:var(--accent-dark) !important; font-weight:600;
  margin-top:6px; border:1px solid rgba(59,130,246,0.08);
}

/* ═══════ MOBILE ═══════ */
@media (max-width:900px){
  .wrap{ display:block; }
  .deck-toggle-btn{ display:inline-flex; position:relative; z-index:1000000; }
  .left-panel{
    position:fixed !important; top:148px !important; left:0 !important;
    width:84vw; max-width:360px; height:calc(100dvh - 148px) !important;
    background:rgba(255,255,255,0.96); backdrop-filter:blur(20px);
    z-index:999999; transform:translateX(-110%);
    transition:transform .3s cubic-bezier(.23,1,.32,1);
    box-shadow:10px 0 40px rgba(15,23,42,0.12);
    border-top-right-radius:22px; border-bottom-right-radius:22px;
    padding:20px 16px !important; border:none;
  }
  .left-panel.open{ transform:translateX(0); }
  #deck-list{ grid-template-columns:1fr; overflow-y:auto; max-height:calc(100dvh - 200px); -webkit-overflow-scrolling:touch; gap:8px; }
  body::after{
    content:""; position:fixed; inset:0;
    background:rgba(15,23,42,0.3); backdrop-filter:blur(2px);
    opacity:0; pointer-events:none; transition:opacity .25s ease; z-index:999998;
  }
  body.sidebar-open::after{ opacity:1; pointer-events:auto; }
  .term{ font-size:38px; line-height:1.35; }
  .meaning{ font-size:28px; }
  .flashcard{ min-height:360px; }
  .controls-top{ display:block !important; }
  .controls-row{ width:100%; margin-bottom:8px; }
  .controls-row-toggle #deck-toggle{ width:100% !important; display:flex !important; justify-content:center; }
  .controls-row-study{ display:flex; gap:8px; }
  .controls-row-study .btn{ flex:1 1 50%; }
  .controls-row-info #deck-info{ font-size:13px; opacity:.85; }
  .flip-hint{ font-size:11px; margin-top:8px; }
  .nav-big{ padding:12px; font-size:15px; border-radius:12px; }
  .level-tabs{ flex-wrap:wrap; }
}

/* ═══════ SCROLLBAR ═══════ */
::-webkit-scrollbar{ width:5px; }
::-webkit-scrollbar-track{ background:transparent; }
::-webkit-scrollbar-thumb{ background:var(--sky); border-radius:10px; }
::-webkit-scrollbar-thumb:hover{ background:var(--accent); }
/* ═══════════════════════════════════════════════════
   AI IMAGE GENERATION — nút tạo hình minh hoạ
   ═══════════════════════════════════════════════════ */

/* Wrapper nằm dưới .term, trên .audio-in-card */
.ai-img-btn-wrap {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  top: 14px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  z-index: 4;
  pointer-events: none; /* wrap không block click card, chỉ button mới bắt */
}

/* Hình SVG được generate */
.ai-img-box {
  width: 140px;
  height: 140px;
  border-radius: 16px;
  overflow: hidden;
  border: 1.5px solid rgba(125, 211, 252, 0.25);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
  background: #172554;
  pointer-events: none;
  animation: ai-img-appear 0.4s cubic-bezier(.23,1,.32,1);
}
.ai-img-box svg {
  width: 100%;
  height: 100%;
  display: block;
}
@keyframes ai-img-appear {
  from { opacity: 0; transform: scale(0.88); }
  to   { opacity: 1; transform: scale(1); }
}

/* Nút tạo hình chính */
.ai-gen-btn {
  pointer-events: all;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 16px;
  border-radius: 20px;
  border: 1.5px solid rgba(125, 211, 252, 0.4);
  background: rgba(23, 37, 84, 0.75);
  backdrop-filter: blur(10px);
  color: #7DD3FC;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(.4,0,.2,1);
  white-space: nowrap;
  font-family: "Noto Sans KR", sans-serif;
  box-shadow: 0 2px 12px rgba(59, 130, 246, 0.15);
}
.ai-gen-btn:hover:not(:disabled) {
  background: rgba(59, 130, 246, 0.35);
  border-color: #7DD3FC;
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 18px rgba(59, 130, 246, 0.3);
}
.ai-gen-btn:active:not(:disabled) {
  transform: scale(0.96);
}
.ai-gen-btn:disabled {
  cursor: not-allowed;
  opacity: 0.65;
}

/* Nút tạo lại (nhỏ, nằm dưới hình) */
.ai-gen-btn.ai-gen-regen {
  padding: 4px 12px;
  font-size: 11px;
  border-radius: 12px;
  opacity: 0.7;
}
.ai-gen-btn.ai-gen-regen:hover:not(:disabled) {
  opacity: 1;
}

/* Icon loading spinner */
.ai-gen-spinner {
  width: 12px;
  height: 12px;
  border: 2px solid rgba(125, 211, 252, 0.3);
  border-top-color: #7DD3FC;
  border-radius: 50%;
  animation: ai-spin 0.7s linear infinite;
  flex-shrink: 0;
}
@keyframes ai-spin {
  to { transform: rotate(360deg); }
}

/* Đẩy .term xuống khi có hình (dùng padding-top trên fc-front khi có ảnh) */
.fc-front:has(.ai-img-box) .term {
  top: auto;
  bottom: 72px; /* phía trên audio button */
  transform: translateX(-50%);
  left: 50%;
  font-size: 36px;
}

/* Mobile */
@media (max-width: 900px) {
  .ai-img-box {
    width: 120px;
    height: 120px;
  }
  .ai-gen-btn {
    font-size: 11px;
    padding: 6px 13px;
  }
  .fc-front:has(.ai-img-box) .term {
    font-size: 30px;
    bottom: 64px;
  }
}