/* ============================================================
   MERMAID SHOW & TELL — Ocean Theme CSS
   ============================================================ */

:root {
  --ocean-deep: #0a2e3f;
  --ocean-mid: #0d4a6b;
  --ocean-light: #1a7aaf;
  --seafoam: #fff;
  --seafoam-light: #fff;
  --coral: #ff6b6b;
  --coral-light: #ff9a9a;
  --pearl: #edf6ff;
  --pearl-bright: #ffffff;
  --gold: #ffd700;
  --gold-light: #fff0a0;
  --lavender: #b8e0f7;
  --sand: #fff9e6;
  --text-dark: #0a2e3f;
  --text-mid: #1a5a7a;
  --text-light: #4a8fa8;
  --radius-sm: 8px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-xl: 36px;
  --shadow-sm: 0 2px 8px rgba(10, 46, 63, 0.12);
  --shadow-md: 0 6px 20px rgba(10, 46, 63, 0.18);
  --shadow-lg: 0 12px 40px rgba(10, 46, 63, 0.25);
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: "Nunito", "Chiron GoRound TC", sans-serif;
  background:
    linear-gradient(rgba(4, 18, 32, 0.1), rgba(4, 18, 32, 0.1)),
    url("images/bg.webp") center center / cover fixed;
  min-height: 100vh;
  color: var(--text-dark);
  overflow-x: hidden;
}

.hidden {
  display: none !important;
}
.page {
  display: none;
}
.page.active {
  display: block;
}

/* ============================================================
   FLOATING BUBBLES BACKGROUND
   ============================================================ */
.bubbles-bg {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

.bubble {
  position: absolute;
  bottom: -60px;
  border-radius: 50%;
  background: radial-gradient(
    circle at 35% 35%,
    rgba(255, 255, 255, 0.6),
    rgba(78, 205, 196, 0.15)
  );
  border: 1px solid rgba(255, 255, 255, 0.3);
  animation: floatUp linear infinite;
  opacity: 0;
}

@keyframes floatUp {
  0% {
    transform: translateX(0) translateY(0) scale(1);
    opacity: 0;
  }
  10% {
    opacity: 0.6;
  }
  90% {
    opacity: 0.3;
  }
  100% {
    transform: translateX(var(--drift)) translateY(-110vh) scale(0.6);
    opacity: 0;
  }
}

/* ============================================================
   SPLASH SCREEN
   ============================================================ */
.splash-screen {
  position: fixed;
  inset: 0;
  z-index: 1000;
  background:
    linear-gradient(rgba(4, 18, 32, 0.55), rgba(4, 18, 32, 0.55)),
    url("images/bg.webp") center center / cover;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow: hidden;
}

.splash-waves {
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 200px;
  pointer-events: none;
}

.wave {
  position: absolute;
  bottom: 0;
  left: -100%;
  width: 300%;
  height: 100px;
  border-radius: 46%;
  animation: waveAnim linear infinite;
}

.wave1 {
  background: rgba(78, 205, 196, 0.25);
  animation-duration: 6s;
  bottom: 10px;
}
.wave2 {
  background: rgba(78, 205, 196, 0.15);
  animation-duration: 9s;
  animation-delay: -2s;
  bottom: 0;
}
.wave3 {
  background: rgba(78, 205, 196, 0.1);
  animation-duration: 12s;
  animation-delay: -4s;
  bottom: -10px;
}

@keyframes waveAnim {
  0% {
    transform: translateX(0) rotate(0deg);
  }
  100% {
    transform: translateX(33.33%) rotate(360deg);
  }
}

.splash-content {
  position: relative;
  z-index: 2;
  padding: 2rem;
}

.splash-mermaid {
  height: clamp(200px, 38vw, 300px);
  width: auto;
  max-width: 90vw;
  animation: mermaidBob 3s ease-in-out infinite;
  display: block;
  margin: 0 auto 1.2rem;
  border-radius: 20px;
  object-fit: contain;
  filter: drop-shadow(0 0 30px rgba(78, 205, 196, 0.6));
}

@keyframes mermaidBob {
  0%,
  100% {
    transform: translateY(0) rotate(-3deg);
  }
  50% {
    transform: translateY(-16px) rotate(3deg);
  }
}

.splash-title {
  font-family: "Fredoka One";
  font-size: clamp(2.4rem, 8vw, 4.5rem);
  color: var(--seafoam);
  text-shadow:
    0 0 30px rgba(78, 205, 196, 0.5),
    2px 4px 0 rgba(0, 0, 0, 0.3);
  letter-spacing: 2px;
  line-height: 1.1;
}

.splash-subtitle {
  font-family: "Nunito", sans-serif;
  font-size: clamp(1rem, 3.5vw, 1.5rem);
  color: var(--lavender);
  font-weight: 700;
  margin-top: 0.4rem;
  margin-bottom: 0.6rem;
}

.splash-desc {
  font-size: clamp(0.8rem, 2.5vw, 1rem);
  color: rgba(255, 255, 255, 0.65);
  margin-bottom: 1.4rem;
}

.splash-fish {
  font-size: clamp(1.3rem, 4vw, 2rem);
  margin-bottom: 2rem;
  animation: fishSwim 2s ease-in-out infinite alternate;
  letter-spacing: 8px;
}

@keyframes fishSwim {
  0% {
    letter-spacing: 6px;
  }
  100% {
    letter-spacing: 14px;
  }
}

.splash-btn {
  font-family: "Fredoka One";
  font-size: clamp(1.1rem, 3.5vw, 1.4rem);
  background: linear-gradient(135deg, var(--seafoam), var(--ocean-light));
  color: white;
  border: none;
  padding: 0.9rem 2.8rem;
  border-radius: 999px;
  cursor: pointer;
  box-shadow:
    0 6px 20px rgba(78, 205, 196, 0.5),
    inset 0 1px 0 rgba(255, 255, 255, 0.3);
  transition:
    transform 0.2s,
    box-shadow 0.2s;
  letter-spacing: 1px;
}

.splash-btn:hover {
  transform: translateY(-3px) scale(1.04);
  box-shadow: 0 10px 30px rgba(78, 205, 196, 0.6);
}

.splash-btn:active {
  transform: translateY(0) scale(0.98);
}

/* ============================================================
   HEADER
   ============================================================ */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(135deg, var(--ocean-deep), var(--ocean-mid));
  box-shadow: var(--shadow-md);
  border-bottom: 2px solid rgba(78, 205, 196, 0.3);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1.5rem;
  max-width: 1100px;
  margin: 0 auto;
  gap: 1rem;
}

.home-btn {
  font-family: "Fredoka One";
  font-size: clamp(1rem, 3vw, 1.3rem);
  background: none;
  border: none;
  color: var(--seafoam);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-shadow: 0 0 12px rgba(78, 205, 196, 0.4);
  transition: color 0.2s;
  white-space: nowrap;
}

.home-btn span {
  color: white;
  font-family: "Fredoka One";
}
.home-btn:hover {
  color: var(--seafoam-light);
}

.topic-count {
  font-family: "Nunito", sans-serif;
  font-size: 0.85rem;
  color: var(--lavender);
  background: rgba(255, 255, 255, 0.1);
  border-radius: 999px;
  padding: 0.2rem 0.8rem;
  white-space: nowrap;
}

/* ============================================================
   HOME PAGE — HERO
   ============================================================ */
#mainApp {
  position: relative;
  z-index: 1;
}

.home-hero {
  text-align: center;
  padding: clamp(2rem, 6vw, 4rem) 1.5rem clamp(1.5rem, 4vw, 3rem);
  position: relative;
  overflow: hidden;
}

.hero-bubbles {
  display: none;
}

@keyframes heroBob {
  0%,
  100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-12px);
  }
}

.hero-title {
  font-family: "Fredoka One";
  display: flex;
  flex-direction: column;
  line-height: 1.15;
  gap: 0.1rem;
}

.title-line1 {
  font-size: clamp(1.4rem, 5vw, 2.2rem);
  color: #dff0ff;
  text-shadow: 0 1px 8px rgba(0, 0, 0, 0.5);
}

.title-line2 {
  font-size: clamp(1.8rem, 6vw, 3rem);
  /* color: var(--seafoam); */
  color: #fff;
  text-shadow:
    0 0 20px rgba(78, 205, 196, 0.5),
    0 2px 8px rgba(0, 0, 0, 0.5);
}

.hero-sub {
  font-size: clamp(0.85rem, 2.5vw, 1rem);
  color: rgba(255, 255, 255, 1);
  margin-top: 0.6rem;
  margin-bottom: 0.8rem;
  font-weight: 600;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.5);
}

.hero-icons {
  font-size: clamp(1.2rem, 3.5vw, 1.8rem);
  letter-spacing: 6px;
  margin-top: 0.4rem;
}

/* ============================================================
   CATEGORIES SECTION
   ============================================================ */
.categories-section {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem 3rem;
}

.section-title {
  font-family: "Fredoka One";
  background: var(--ocean-deep);
  font-size: clamp(1.2rem, 4vw, 1.6rem);
  color: var(--seafoam-light);
  display: flex;
  align-items: center;
  gap: 0.6rem;
  border-radius: var(--radius-lg);
  margin-bottom: 1.2rem;
  padding: 0.6rem;
  border-bottom: 2px solid rgba(78, 205, 196, 0.25);
}

.shell-icon {
  animation: shellSpin 6s linear infinite;
  display: inline-block;
}
@keyframes shellSpin {
  0%,
  80% {
    transform: rotate(0deg);
  }
  85% {
    transform: rotate(360deg);
  }
  100% {
    transform: rotate(360deg);
  }
}

.categories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.2rem;
}

.category-card {
  background: linear-gradient(
    135deg,
    rgba(10, 35, 60, 0.72),
    rgba(5, 25, 45, 0.65)
  );
  border: 1px solid rgba(78, 205, 196, 0.25);
  border-radius: var(--radius-lg);
  padding: 1.4rem 1.6rem;
  cursor: pointer;
  transition:
    transform 0.25s,
    box-shadow 0.25s,
    border-color 0.25s,
    background 0.25s;
  backdrop-filter: blur(6px);
  position: relative;
  overflow: hidden;
}

.category-card::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: linear-gradient(135deg, rgba(78, 205, 196, 0.12), transparent);
  opacity: 0;
  transition: opacity 0.3s;
}

.category-card:hover::before {
  opacity: 1;
}

.category-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 30px rgba(78, 205, 196, 0.25);
  border-color: rgba(78, 205, 196, 0.5);
}

.category-card:active {
  transform: translateY(-1px);
}

.cat-emoji {
  font-size: 2.2rem;
  display: block;
  margin-bottom: 0.5rem;
}

.cat-name-zh {
  font-size: 0.85rem;
  color: #c8e8ff;
  font-weight: 700;
  margin-bottom: 0.15rem;
}

.cat-name-en {
  font-family: "Fredoka One";
  font-size: 1.1rem;
  color: var(--seafoam-light);
  margin-bottom: 0.5rem;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
}

.cat-count {
  font-size: 0.78rem;
  color: rgba(255, 255, 255, 0.7);
  background: rgba(255, 255, 255, 0.12);
  border-radius: 999px;
  padding: 0.15rem 0.6rem;
  display: inline-block;
}

/* ============================================================
   PAGE NAVIGATION
   ============================================================ */
.page-nav {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.5rem;
  max-width: 1100px;
  margin: 0 auto;
  flex-wrap: wrap;
}

.back-btn {
  font-family: "Nunito", sans-serif;
  font-size: 0.9rem;
  font-weight: 700;
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(78, 205, 196, 0.3);
  color: var(--seafoam-light);
  padding: 0.45rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  transition:
    background 0.2s,
    transform 0.15s;
  white-space: nowrap;
}

.back-btn:hover {
  background: rgba(78, 205, 196, 0.2);
  transform: translateX(-2px);
}

.page-title {
  font-family: "Fredoka One";
  font-size: clamp(1.1rem, 4vw, 1.6rem);
  color: var(--seafoam-light);
  flex: 1;
}

/* Topic nav arrows */
.topic-nav-btns {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-left: auto;
}

.nav-arrow {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: 1.5px solid rgba(78, 205, 196, 0.4);
  background: rgba(255, 255, 255, 0.08);
  color: var(--seafoam);
  font-size: 1.4rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition:
    background 0.2s,
    transform 0.15s;
  line-height: 1;
}
.nav-arrow:hover:not(:disabled) {
  background: rgba(78, 205, 196, 0.25);
  transform: scale(1.1);
}
.nav-arrow:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

.nav-label {
  font-size: 0.78rem;
  color: rgba(255, 255, 255, 0.5);
  white-space: nowrap;
  min-width: 60px;
  text-align: center;
}

/* ============================================================
   TOPICS GRID
   ============================================================ */
.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1rem;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem 3rem;
}

.topic-card-thumb {
  background: linear-gradient(
    135deg,
    rgba(10, 35, 60, 0.72),
    rgba(5, 25, 45, 0.65)
  );
  border: 1px solid rgba(78, 205, 196, 0.2);
  border-radius: var(--radius-md);
  padding: 1.1rem 1.2rem;
  cursor: pointer;
  transition:
    transform 0.2s,
    box-shadow 0.2s,
    border-color 0.2s;
  position: relative;
  overflow: hidden;
}

.topic-card-thumb::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--seafoam), var(--coral));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s;
}

.topic-card-thumb:hover::after {
  transform: scaleX(1);
}

.topic-card-thumb:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(78, 205, 196, 0.2);
  border-color: rgba(78, 205, 196, 0.4);
}

.thumb-num {
  font-size: 0.72rem;
  color: rgba(255, 255, 255, 0.35);
  font-weight: 800;
  margin-bottom: 0.3rem;
}

.thumb-title {
  font-family: "Fredoka One";
  font-size: 1rem;
  color: #ffffff;
  line-height: 1.3;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
}

/* ============================================================
   TOPIC DETAIL CARD
   ============================================================ */
.topic-card {
  max-width: 820px;
  margin: 0 auto;

  background: linear-gradient(
    135deg,
    rgba(8, 30, 52, 0.42),
    rgba(5, 20, 38, 0.2)
  );
  padding: 1.5rem;
  border-radius: var(--radius-xl) var(--radius-xl) var(--radius-md)
    var(--radius-md);
  backdrop-filter: blur(4px);
}

.topic-card-header {
  background: linear-gradient(
    135deg,
    rgba(8, 30, 52, 0.82),
    rgba(5, 20, 38, 0.78)
  );
  border: 1px solid rgba(78, 205, 196, 0.3);
  border-radius: var(--radius-xl) var(--radius-xl) var(--radius-md)
    var(--radius-md);
  padding: 1.8rem 2rem 1.4rem;
  margin-bottom: 0.8rem;
  position: relative;
  overflow: hidden;
}

.topic-card-header::before {
  content: "🌊";
  position: absolute;
  right: 1.5rem;
  top: 1rem;
  font-size: 3.5rem;
  opacity: 0.08;
  pointer-events: none;
}

.topic-category-tag {
  font-size: 0.78rem;
  font-weight: 800;
  color: var(--coral-light);
  background: rgba(255, 107, 107, 0.15);
  border: 1px solid rgba(255, 107, 107, 0.3);
  border-radius: 999px;
  padding: 0.2rem 0.8rem;
  display: inline-block;
  margin-bottom: 0.6rem;
  letter-spacing: 0.5px;
}

.topic-main-title {
  font-family: "Fredoka One";
  font-size: clamp(2rem, 5vw, 2.4rem);
  color: white;
  margin-bottom: 1rem;
  text-shadow: 0 2px 12px rgba(78, 205, 196, 0.3);
}

.topic-tools {
  display: flex;
  gap: 0.7rem;
  flex-wrap: wrap;
}

.tool-btn {
  font-family: "Nunito", sans-serif;
  font-size: 0.9rem;
  font-weight: 800;
  padding: 0.5rem 1.1rem;
  border-radius: 999px;
  border: none;
  cursor: pointer;
  transition:
    transform 0.2s,
    box-shadow 0.2s,
    opacity 0.2s;
}

.speak-all-btn {
  background: linear-gradient(135deg, var(--seafoam), var(--ocean-light));
  color: white;
  box-shadow: 0 3px 12px rgba(78, 205, 196, 0.35);
}

.speak-all-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 18px rgba(78, 205, 196, 0.45);
}
.speak-all-btn.speaking {
  animation: speakPulse 1.2s ease-in-out infinite;
}

@keyframes speakPulse {
  0%,
  100% {
    box-shadow: 0 3px 12px rgba(78, 205, 196, 0.35);
  }
  50% {
    box-shadow: 0 3px 24px rgba(78, 205, 196, 0.7);
  }
}

.tool-btn:not(.speak-all-btn) {
  background: rgba(255, 255, 255, 0.1);
  border: 1.5px solid rgba(78, 205, 196, 0.3);
  color: var(--seafoam-light);
}

.tool-btn:not(.speak-all-btn):hover {
  background: rgba(78, 205, 196, 0.18);
  transform: translateY(-1px);
}

/* ============================================================
   LINES / SENTENCES
   ============================================================ */
.lines-container {
  display: flex;
  flex-direction: column;
  gap: 0;
  padding: 0.5rem 0;
  background: rgba(4, 18, 35, 0.45);
  border-radius: var(--radius-md);
}

.line-item {
  padding: 1rem 1.2rem;
  cursor: pointer;
  transition: background 0.18s;
  border-bottom: 1px solid rgba(78, 205, 196, 0.12);
  margin-bottom: 2px;
}

.line-item:last-child {
  border-bottom: none;
}

.line-item:hover {
  background: rgba(78, 205, 196, 0.06);
}

.line-item.highlighted {
  background: rgba(78, 205, 196, 0.13);
  box-shadow: inset 3px 0 0 var(--seafoam);
}

.line-en {
  font-size: clamp(1.25rem, 3.2vw, 1.5rem);
  font-weight: 700;
  color: white;
  line-height: 1.6;
}

.line-zh {
  font-size: clamp(0.82rem, 2.5vw, 0.92rem);
  color: rgba(184, 224, 247, 0.72);
  font-weight: 600;
  line-height: 1.5;
  margin-top: 0.3rem;
  display: none;
}

.line-zh.visible {
  display: block;
}

/* ============================================================
   TOPIC CARD FOOTER
   ============================================================ */
.topic-card-footer {
  margin-top: 1.2rem;
  display: flex;
  flex-direction: column;
  gap: 0.7rem;
}

.tips-box {
  background: rgba(255, 215, 0, 0.08);
  border: 1px solid rgba(255, 215, 0, 0.25);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.2rem;
  display: flex;
  gap: 0.7rem;
  align-items: flex-start;
}

.tips-icon {
  font-size: 1.1rem;
  flex-shrink: 0;
  margin-top: 0.05rem;
}
.tips-text {
  font-size: 0.85rem;
  color: rgba(255, 240, 160, 0.85);
  font-weight: 600;
  line-height: 1.5;
}

.audio-note {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.4);
  padding: 0 0.2rem;
}

/* ============================================================
   WAVE DIVIDERS
   ============================================================ */
.wave-divider {
  width: 100%;
  height: 40px;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 1200 40'%3E%3Cpath d='M0 20 Q150 0 300 20 Q450 40 600 20 Q750 0 900 20 Q1050 40 1200 20 L1200 40 L0 40 Z' fill='rgba(78,205,196,0.15)'/%3E%3C/svg%3E")
    repeat-x;
  background-size: 600px 40px;
  pointer-events: none;
}

/* ============================================================
   SCROLLBAR
   ============================================================ */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: var(--ocean-deep);
}
::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--seafoam), var(--ocean-light));
  border-radius: 4px;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 600px) {
  .categories-grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.8rem;
  }
  .topics-grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.8rem;
  }
  .topic-card-header {
    padding: 1.2rem 1.2rem 1rem;
  }
  .topic-card {
    padding: 1rem;
  }
  .page-nav {
    padding: 0.8rem 1rem;
    gap: 0.6rem;
  }
  .home-hero {
    padding: 1.5rem 1rem 1.2rem;
  }
  .categories-section {
    padding: 0 1rem 2.5rem;
  }
  .header-inner {
    padding: 0.6rem 1rem;
  }
  .home-btn span {
    display: none;
  }
}

@media (max-width: 380px) {
  .categories-grid {
    grid-template-columns: 1fr;
  }
  .topics-grid {
    grid-template-columns: 1fr;
  }
}

/* ============================================================
   ANIMATIONS / UTILITIES
   ============================================================ */
.fade-in {
  animation: fadeIn 0.4s ease both;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.slide-in {
  animation: slideIn 0.35s cubic-bezier(0.22, 0.68, 0, 1.3) both;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* Speaking indicator dots */
.speaking-dots::after {
  content: "...";
  animation: dots 1s steps(3, end) infinite;
}

@keyframes dots {
  0% {
    content: ".";
  }
  33% {
    content: "..";
  }
  66% {
    content: "...";
  }
  100% {
    content: "";
  }
}

/* Coral underline on active category */
.category-card.active {
  border-color: rgba(255, 107, 107, 0.5);
  background: linear-gradient(
    135deg,
    rgba(255, 107, 107, 0.1),
    rgba(255, 107, 107, 0.04)
  );
}

/* Hero illustration */
.hero-illustration {
  margin: 1.6rem auto 0;
  max-width: min(260px, 65vw);
}
.hero-illustration img {
  width: 100%;
  border-radius: 20px;
  /* box-shadow:
    0 16px 40px rgba(10, 46, 63, 0.5),
    0 0 0 3px rgba(78, 205, 196, 0.2); */
  animation: mermaidBob 4s ease-in-out infinite;
}

/* Topic decorative image */
.topic-deco-img {
  border-radius: var(--radius-md);
  overflow: hidden;
  height: 130px;
  margin-top: 0.4rem;
}
.topic-deco-img img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 25%;
  opacity: 0.65;
  transition: opacity 0.3s;
}
.topic-deco-img:hover img {
  opacity: 0.85;
}

/* Minimax TTS note */
.tts-badge {
  position: fixed;
  bottom: 1.2rem;
  right: 1.2rem;
  background: rgba(10, 46, 63, 0.85);
  border: 1px solid rgba(78, 205, 196, 0.3);
  border-radius: var(--radius-md);
  padding: 0.5rem 0.9rem;
  font-size: 0.72rem;
  color: rgba(184, 224, 247, 0.75);
  z-index: 200;
  backdrop-filter: blur(8px);
  pointer-events: none;
}