/* ============================================
   QMFS 2026 - Modern Academic Conference Website
   Stylesheet: Modern, Clean, Professional
   ============================================ */

/* ========== CSS Variables & Theme ========== */
:root {
  /* Color Palette - Tươi nhưng không sặc sỡ */
  --primary: #2563eb; /* Blue - chuyên nghiệp */
  --primary-dark: #1e40af;
  --primary-light: #3b82f6;
  --secondary: #10b981; /* Green - khoa học */
  --accent: #f59e0b; /* Amber - điểm nhấn */

  /* Neutral Colors */
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-light: #94a3b8;
  --bg-white: #ffffff;
  --bg-light: #f8fafc;
  --bg-gradient-start: #f0f9ff;
  --bg-gradient-end: #f0fdfa;

  /* Glassmorphism */
  --glass-bg: rgba(255, 255, 255, 0.7);
  --glass-border: rgba(255, 255, 255, 0.18);
  --glass-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);

  /* Typography */
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-heading: 'Poppins', var(--font-primary);

  /* Spacing */
  --section-padding: 80px 0;
  --section-padding-mobile: 50px 0;

  /* Transitions */
  --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-bounce: all 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

/* ========== Base Styles ========== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-primary);
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--bg-white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.2;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

h1 {
  font-size: clamp(2rem, 4.5vw, 3.5rem);
}
h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
}
h3 {
  font-size: clamp(1.25rem, 2.5vw, 1.75rem);
}
h4 {
  font-size: clamp(1.1rem, 2vw, 1.35rem);
}

p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition-smooth);
}

a:hover {
  color: var(--primary-dark);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* ========== Utility Classes ========== */
.section {
  padding: var(--section-padding);
  position: relative;
}

@media (max-width: 768px) {
  .section {
    padding: var(--section-padding-mobile);
  }
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

.text-center {
  text-align: center;
}

.mb-4 {
  margin-bottom: 2rem;
}
.mb-5 {
  margin-bottom: 3rem;
}
.mt-5 {
  margin-top: 3rem;
}

/* Gradient Text */
.gradient-text {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Glassmorphism Card */
.glass-card {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-radius: 20px;
  border: 1px solid var(--glass-border);
  box-shadow: var(--glass-shadow);
  padding: 2rem;
  transition: var(--transition-smooth);
}

.glass-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 12px 40px 0 rgba(31, 38, 135, 0.5);
}

/* Contact Information - No background, vertically centered */
.contact-info-wrapper {
  padding: 2rem 0;
  background: transparent;
  border: none;
  box-shadow: none;
  min-height: 100%;
}

.contact-info-wrapper:hover {
  transform: none;
  box-shadow: none;
}

/* ========== Header & Navigation ========== */
.navbar {
  padding: 1.5rem 0;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: 0 2px 20px rgba(0, 0, 0, 0.05);
  position: sticky;
  top: 0;
  z-index: 1000;
  transition: var(--transition-smooth);
}

.navbar.scrolled {
  padding: 1rem 0;
  box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
}

.navbar-brand img {
  max-height: 50px;
}

.nav-link {
  font-weight: 500;
  color: var(--text-primary) !important;
  margin: 0 0.5rem;
  padding: 0.5rem 1rem !important;
  border-radius: 8px;
  transition: var(--transition-smooth);
}

.nav-link:hover {
  background: var(--bg-light);
  color: var(--primary) !important;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  border: none;
  padding: 0.65rem 1.75rem;
  border-radius: 50px;
  font-weight: 600;
  font-size: 0.9rem;
  color: white;
  transition: var(--transition-bounce);
  box-shadow: 0 4px 15px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
  color: white;
}

.btn-outline-primary {
  border: 2px solid var(--primary);
  color: var(--primary);
  padding: 0.65rem 1.75rem;
  border-radius: 50px;
  font-weight: 600;
  font-size: 0.9rem;
  background: transparent;
  transition: var(--transition-smooth);
}

.btn-outline-primary:hover {
  background: var(--primary);
  color: white;
  transform: translateY(-2px);
}

/* ========== Hero Section ========== */
.hero-section {
  min-height: 85vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  background: linear-gradient(
      rgba(255, 255, 255, 0.7) 0%,
      rgba(240, 249, 255, 0.6) 30%,
      rgba(240, 253, 250, 0.6) 70%,
      rgba(255, 255, 255, 0.7) 100%
    ),
    url('assets/images/background.png');
  background-size: 200% 200%, cover;
  background-position: 50% 50%, center center;
  background-repeat: no-repeat, no-repeat;
  background-attachment: fixed, fixed;
  padding: 90px 0 60px;
  transition: background-position 0.5s ease-out;
}

/* Mouse-following background layers */
.hero-section::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(37, 99, 235, 0.08) 0%, transparent 60%);
  transform-origin: center center;
  transform: translate(calc((var(--mouse-x, 50) - 50) * 0.5%), calc((var(--mouse-y, 50) - 50) * 0.5%))
    rotate(var(--mouse-angle, 0deg));
  z-index: 0;
  transition: transform 0.6s ease-out;
  pointer-events: none;
}

.hero-section::after {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(16, 185, 129, 0.06) 0%, transparent 70%);
  transform-origin: center center;
  transform: translate(calc((50 - var(--mouse-x, 50)) * 0.5%), calc((50 - var(--mouse-y, 50)) * 0.5%))
    rotate(calc(-1 * var(--mouse-angle, 0deg)));
  z-index: 0;
  transition: transform 0.6s ease-out;
  pointer-events: none;
}

@keyframes heroGradientShift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@keyframes heroRotateBackground {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

@keyframes heroRotateBackgroundReverse {
  from {
    transform: rotate(360deg);
  }
  to {
    transform: rotate(0deg);
  }
}

@keyframes heroGridMove {
  0% {
    background-position: 0% 50%, 0 0;
  }
  100% {
    background-position: 0% 50%, 100px 100px;
  }
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-block;
  padding: 0.45rem 1.25rem;
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border-radius: 50px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--primary);
  margin-bottom: 1.25rem;
  border: 1px solid var(--glass-border);
  animation: fadeInUp 0.6s ease-out;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 4rem);
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: 1.25rem;
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--primary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: fadeInUp 0.8s ease-out 0.2s both;
}

.hero-subtitle {
  font-size: clamp(0.9rem, 1.8vw, 1.1rem);
  color: var(--text-secondary);
  margin-bottom: 1.75rem;
  animation: fadeInUp 1s ease-out 0.4s both;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  animation: fadeInUp 1.2s ease-out 0.6s both;
}

.hero-image {
  position: relative;
  z-index: 1;
}

.hero-image img {
  border-radius: 30px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.2);
  animation: fadeInRight 1s ease-out 0.8s both;
}

/* Countdown Timer */
.countdown-container {
  margin-top: 3rem;
  padding: 2rem 1.5rem;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(15px);
  -webkit-backdrop-filter: blur(15px);
  border-radius: 20px;
  border: 1px solid rgba(255, 255, 255, 0.3);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

.countdown-item {
  text-align: center;
  padding: 0.75rem;
  margin-bottom: 0;
}

.countdown-circle-wrapper {
  position: relative;
  display: inline-block;
  width: 120px;
  height: 120px;
  margin: 0 auto;
}

.progress-ring {
  transform: rotate(-90deg);
  transform-origin: 50% 50%;
  width: 120px;
  height: 120px;
}

.progress-ring__circle {
  transition: stroke-dashoffset 0.5s ease-out;
  stroke-linecap: round;
  transform-origin: 50% 50%;
}

.progress-ring__circle-bg {
  fill: transparent;
}

.countdown-text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
  width: 100%;
  pointer-events: none;
  z-index: 1;
}

.countdown-number {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--primary);
  display: block;
  line-height: 1.1;
  margin-bottom: 0.25rem;
}

.countdown-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-secondary);
  font-weight: 600;
  margin: 0;
  line-height: 1.2;
}

@media (max-width: 768px) {
  .countdown-container {
    padding: 1.5rem 1rem;
    margin-top: 2rem;
  }

  .countdown-item {
    padding: 0.5rem;
  }

  .countdown-circle-wrapper {
    width: 100px;
    height: 100px;
  }

  .progress-ring {
    width: 100px;
    height: 100px;
  }

  .countdown-number {
    font-size: 1.5rem;
  }

  .countdown-label {
    font-size: 0.65rem;
  }
}

/* ========== About Section ========== */
.about-section {
  background: var(--bg-white);
  overflow: hidden;
}

.section-header {
  text-align: center;
  max-width: 750px;
  margin: 0 auto 3rem;
}

.section-badge {
  display: inline-block;
  padding: 0.45rem 1.25rem;
  background: linear-gradient(135deg, var(--primary-light), var(--secondary));
  color: white;
  border-radius: 50px;
  font-size: 0.8rem;
  font-weight: 600;
  margin-bottom: 0.875rem;
}

.section-title {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
  margin-bottom: 0.875rem;
}

.section-description {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.about-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
}

@media (max-width: 968px) {
  .about-content {
    grid-template-columns: 1fr;
    gap: 2rem;
  }
}

.about-image {
  position: relative;
}

.about-image img {
  border-radius: 20px;
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.1);
}

.about-stats {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
  margin-top: 1.75rem;
}

.stat-item {
  text-align: center;
  padding: 1.25rem;
  background: var(--bg-light);
  border-radius: 12px;
  transition: var(--transition-smooth);
}

.stat-item:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
}

.stat-number {
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--primary);
  display: block;
  margin-bottom: 0.4rem;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* ========== Topics Section ========== */
.topics-section {
  background: var(--bg-light);
  background-image: url('assets/images/background-topic.png');
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
  background-attachment: fixed;
  position: relative;
  overflow: hidden;
}

/* Overlay để đảm bảo nội dung dễ đọc */
.topics-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255, 255, 255, 0.85);
  z-index: 0;
}

.topics-section .container {
  position: relative;
  z-index: 1;
}

.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
}

.topic-card {
  background: var(--bg-white);
  border-radius: 18px;
  padding: 2rem;
  box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
  transition: var(--transition-smooth);
  border: 1px solid transparent;
  height: 100%;
  display: flex;
  flex-direction: column;
}

.topic-card:hover {
  transform: translateY(-10px);
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.15);
  border-color: var(--primary-light);
}

.topic-icon {
  width: 55px;
  height: 55px;
  background: linear-gradient(135deg, var(--primary-light), var(--secondary));
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
  font-size: 1.35rem;
  color: white;
}

.topic-title {
  font-size: 1.1rem;
  margin-bottom: 0.875rem;
  color: var(--text-primary);
}

.topic-description {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
  flex-grow: 1;
}

/* ========== Key Dates Section ========== */
.dates-section {
  background: var(--bg-white);
}

.timeline {
  position: relative;
  max-width: 900px;
  margin: 3rem auto 0;
  padding: 2rem 0;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 30px;
  top: 0;
  bottom: 0;
  width: 4px;
  background: linear-gradient(180deg, var(--primary), var(--secondary));
  border-radius: 2px;
}

.timeline-item {
  position: relative;
  margin-bottom: 4rem;
  display: flex;
  align-items: center;
  width: 100%;
  flex-direction: row;
}

.timeline-content {
  flex: 1;
  background: var(--bg-white);
  padding: 1.75rem;
  border-radius: 18px;
  box-shadow: 0 5px 25px rgba(0, 0, 0, 0.1);
  margin-left: calc(30px + 60px);
  transition: var(--transition-smooth);
  border: 1px solid transparent;
}

.timeline-content:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 35px rgba(0, 0, 0, 0.15);
  border-color: var(--primary-light);
}

@media (max-width: 768px) {
  .timeline-content {
    margin-left: 5rem;
    margin-right: 0;
  }

  .timeline-date {
    right: auto;
    left: 30px;
    transform: translateX(-50%);
  }
}

.timeline-date {
  position: absolute;
  left: 30px;
  transform: translateX(-50%);
  width: 80px;
  height: 80px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-weight: 700;
  font-size: 0.8rem;
  box-shadow: 0 8px 25px rgba(37, 99, 235, 0.3);
  z-index: 2;
  border: 3px solid var(--bg-white);
  text-align: center;
  line-height: 1.2;
}

.timeline-date div {
  font-size: 0.8rem;
}

@media (max-width: 768px) {
  .timeline-date {
    left: 30px;
    transform: translateX(-50%);
    width: 70px;
    height: 70px;
    font-size: 0.75rem;
  }
}

.timeline-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.625rem;
  color: var(--text-primary);
}

.timeline-description {
  color: var(--text-secondary);
  font-size: 0.875rem;
  line-height: 1.6;
  margin: 0;
}

/* ========== Speakers Section ========== */
.speakers-section {
  background: var(--bg-light);
  background-image: url('assets/images/background-keynote.png');
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
  background-attachment: fixed;
  position: relative;
  overflow: hidden;
}

/* Overlay để đảm bảo nội dung dễ đọc */
.speakers-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255, 255, 255, 0.85);
  z-index: 0;
}

.speakers-section .container {
  position: relative;
  z-index: 1;
}

.speakers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 2rem;
}

.speaker-card {
  background: var(--bg-white);
  border-radius: 18px;
  padding: 1.75rem;
  text-align: center;
  box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
  transition: var(--transition-smooth);
  border: 1px solid transparent;
}

.speaker-card:hover {
  transform: translateY(-10px);
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.15);
  border-color: var(--primary-light);
}

.speaker-avatar {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  margin: 0 auto 1.25rem;
  object-fit: cover;
  border: 3px solid var(--primary-light);
  box-shadow: 0 5px 20px rgba(37, 99, 235, 0.2);
}

.speaker-name {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
  color: var(--text-primary);
}

.speaker-title {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 0.875rem;
}

.speaker-bio {
  font-size: 0.8rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ========== Call for Papers Section ========== */
.cfp-section {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 50%, var(--secondary) 100%);
  background-size: 200% 200%;
  background-position: 50% 50%;
  color: white;
  position: relative;
  overflow: hidden;
  transition: background-position 0.5s ease-out;
}

/* Mouse-following background layers */
.cfp-section::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.2) 0%, transparent 60%);
  transform-origin: center center;
  transform: translate(calc((var(--mouse-x, 50) - 50) * 0.5%), calc((var(--mouse-y, 50) - 50) * 0.5%))
    rotate(var(--mouse-angle, 0deg));
  z-index: 0;
  transition: transform 0.6s ease-out;
  pointer-events: none;
}

.cfp-section::after {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(16, 185, 129, 0.25) 0%, transparent 70%);
  transform-origin: center center;
  transform: translate(calc((50 - var(--mouse-x, 50)) * 0.5%), calc((50 - var(--mouse-y, 50)) * 0.5%))
    rotate(calc(-1 * var(--mouse-angle, 0deg)));
  z-index: 0;
  transition: transform 0.6s ease-out;
  pointer-events: none;
}

@keyframes rotateBackground {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

@keyframes rotateBackgroundReverse {
  from {
    transform: rotate(360deg);
  }
  to {
    transform: rotate(0deg);
  }
}

@keyframes gradientShift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

.cfp-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0 auto;
  text-align: center;
}

.cfp-title {
  color: white;
  margin-bottom: 1.25rem;
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
}

.cfp-description {
  font-size: 1rem;
  color: rgba(255, 255, 255, 0.9);
  margin-bottom: 1.75rem;
  line-height: 1.7;
}

.cfp-features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-top: 3rem;
}

.cfp-feature {
  padding: 1.25rem;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.cfp-feature-icon {
  font-size: 1.75rem;
  margin-bottom: 0.875rem;
}

.cfp-feature-title {
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

.cfp-feature-text {
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.8);
}

/* ========== Registration Section ========== */
.registration-section {
  background: var(--bg-white);
}

.registration-card {
  max-width: 550px;
  margin: 0 auto;
  border-radius: 18px;
  padding: 2.5rem;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
  position: relative;
  overflow: hidden;
  background: var(--bg-white);
}

.registration-card > * {
  position: relative;
  z-index: 1;
}

@keyframes registrationGradientShift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@keyframes registrationRotateBackground {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

@keyframes registrationRotateBackgroundReverse {
  from {
    transform: rotate(360deg);
  }
  to {
    transform: rotate(0deg);
  }
}

.registration-form {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.form-group {
  position: relative;
}

/* ========== Form Styles with Floating Labels ========== */
.input-wrapper {
  position: relative;
  display: block;
  width: 100%;
  margin-bottom: 0;
}

.input-icon {
  position: absolute;
  left: 15px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-secondary);
  font-size: 18px;
  z-index: 10;
  transition: var(--transition-smooth);
  pointer-events: none;
  line-height: 1;
}

.textarea-icon {
  top: 18px;
  transform: translateY(0);
}

.form-input {
  width: 100% !important;
  padding: 14px 15px 14px 50px !important;
  border: 2px solid rgba(30, 41, 59, 0.15) !important;
  border-radius: 12px !important;
  font-size: 15px !important;
  background-color: #ffffff !important;
  transition: var(--transition-smooth) !important;
  color: var(--text-primary) !important;
  font-family: var(--font-primary) !important;
  box-sizing: border-box;
}

.form-input::placeholder {
  color: transparent;
}

.form-input:focus {
  outline: none;
  border-color: var(--primary);
  background-color: #ffffff;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
  transform: translateY(-2px);
}

.form-select {
  width: 100% !important;
  padding: 14px 15px 14px 50px !important;
  border: 2px solid rgba(30, 41, 59, 0.15) !important;
  border-radius: 12px !important;
  font-size: 15px !important;
  background-color: #ffffff !important;
  transition: var(--transition-smooth) !important;
  color: var(--text-primary) !important;
  appearance: none;
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3e%3cpath fill='none' stroke='%23343a40' stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M2 5l6 6 6-6'/%3e%3c/svg%3e") !important;
  background-repeat: no-repeat !important;
  background-position: right 15px center !important;
  background-size: 16px 12px !important;
  padding-right: 40px !important;
  font-family: var(--font-primary) !important;
  box-sizing: border-box;
}

.form-select:focus {
  border-color: var(--primary);
  background-color: #ffffff;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
  transform: translateY(-2px);
  outline: none;
}

.form-textarea {
  width: 100% !important;
  padding: 18px 15px 14px 50px !important;
  border: 2px solid rgba(30, 41, 59, 0.15) !important;
  border-radius: 12px !important;
  font-size: 15px !important;
  background-color: #ffffff !important;
  transition: var(--transition-smooth) !important;
  color: var(--text-primary) !important;
  resize: vertical;
  min-height: 120px;
  font-family: var(--font-primary) !important;
  box-sizing: border-box;
}

.form-textarea::placeholder {
  color: transparent;
}

.form-textarea:focus {
  outline: none;
  border-color: var(--primary);
  background-color: #ffffff;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
  transform: translateY(-2px);
}

.form-label {
  position: absolute;
  left: 50px;
  top: 50%;
  transform: translateY(-50%);
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 15px;
  transition: var(--transition-smooth);
  pointer-events: none;
  z-index: 5;
  background-color: #ffffff;
  padding: 0 4px;
  margin: 0;
  white-space: nowrap;
}

/* Floating label effect */
.form-input:focus ~ .form-label,
.form-input:not(:placeholder-shown) ~ .form-label {
  top: 0;
  transform: translateY(-50%) scale(0.85);
  color: var(--primary);
  font-weight: 600;
}

.form-select:focus ~ .form-label,
.form-select.has-value ~ .form-label {
  top: 0;
  transform: translateY(-50%) scale(0.85);
  color: var(--primary);
  font-weight: 600;
}

.form-textarea:focus ~ .form-label,
.form-textarea:not(:placeholder-shown) ~ .form-label {
  top: 0;
  transform: translateY(-50%) scale(0.85);
  color: var(--primary);
  font-weight: 600;
}

.form-textarea ~ .form-label {
  top: 18px;
  transform: translateY(0);
}

/* File input styling */
.form-input[type='file'] {
  padding: 14px 15px 14px 50px;
  cursor: pointer;
}

.form-input[type='file']::-webkit-file-upload-button {
  visibility: hidden;
}

.form-input[type='file']:focus ~ .form-label,
.form-input[type='file']:not(:placeholder-shown) ~ .form-label,
.form-input[type='file'].has-file ~ .form-label {
  top: 0;
  transform: translateY(-50%) scale(0.85);
  color: var(--primary);
  font-weight: 600;
}

/* Icon effects */
.form-group:focus-within .input-icon {
  color: var(--primary) !important;
  transform: scale(1.1) translateY(-50%);
}

.form-input:not(:placeholder-shown) ~ .input-icon,
.form-select.has-value ~ .input-icon,
.form-textarea:not(:placeholder-shown) ~ .input-icon {
  color: var(--primary) !important;
}

.form-input:focus ~ .input-icon,
.form-select:focus ~ .input-icon,
.form-textarea:focus ~ .input-icon {
  color: var(--primary) !important;
  transform: scale(1.1) translateY(-50%);
}

/* Form control base styles - chỉ áp dụng khi không có form-input */
.form-control:not(.form-input):not(.form-select):not(.form-textarea) {
  width: 100%;
  padding: 1rem 1.5rem;
  border: 2px solid transparent;
  border-radius: 12px;
  background: white;
  font-size: 1rem;
  transition: var(--transition-smooth);
  font-family: var(--font-primary);
}

.form-control:not(.form-input):not(.form-select):not(.form-textarea):focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ========== Footer ========== */
.footer {
  background: var(--text-primary);
  color: rgba(255, 255, 255, 0.8);
  padding: 3rem 0 1.5rem;
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2.5rem;
  margin-bottom: 2.5rem;
}

.footer-section h4 {
  color: white;
  margin-bottom: 1.25rem;
  font-size: 1.1rem;
}

.footer-links {
  list-style: none;
  padding: 0;
}

.footer-links li {
  margin-bottom: 0.75rem;
}

.footer-links a {
  color: rgba(255, 255, 255, 0.8);
  transition: var(--transition-smooth);
}

.footer-links a:hover {
  color: white;
  padding-left: 5px;
}

.footer-bottom {
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  color: rgba(255, 255, 255, 0.6);
  font-size: 0.875rem;
}

/* ========== Animations ========== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

.fade-in-up {
  animation: fadeInUp 0.8s ease-out both;
}

/* Scroll Reveal Animation */
.reveal {
  opacity: 0;
  transform: translateY(50px);
  transition: all 0.8s ease-out;
}

.reveal.active {
  opacity: 1;
  transform: translateY(0);
}

/* Reveal với delay khác nhau */
.reveal-delay-1 {
  transition-delay: 0.1s;
}

.reveal-delay-2 {
  transition-delay: 0.2s;
}

.reveal-delay-3 {
  transition-delay: 0.3s;
}

.reveal-delay-4 {
  transition-delay: 0.4s;
}

/* Reveal từ trái và phải */
.reveal-left {
  opacity: 0;
  transform: translateX(-30px);
  transition: all 0.8s ease-out;
}

.reveal-left.active {
  opacity: 1;
  transform: translateX(0);
}

.reveal-right {
  opacity: 0;
  transform: translateX(30px);
  transition: all 0.8s ease-out;
}

.reveal-right.active {
  opacity: 1;
  transform: translateX(0);
}

/* ========== Responsive Design ========== */
@media (max-width: 768px) {
  .hero-section {
    min-height: auto;
    padding: 100px 0 60px;
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .countdown-number {
    font-size: 2rem;
  }

  .topics-grid {
    grid-template-columns: 1fr;
  }

  .speakers-grid {
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  }

  .cfp-features {
    grid-template-columns: 1fr;
  }

  .registration-card {
    padding: 2rem;
  }
}

/* ========== Back to Top Button ========== */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: white;
  border: none;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-smooth);
  z-index: 999;
  box-shadow: 0 5px 20px rgba(37, 99, 235, 0.3);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(37, 99, 235, 0.4);
}

/* ========== Language Toggle Button ========== */
.lang-toggle-btn {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 60px;
  height: 60px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: white;
  border: none;
  border-radius: 50%;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  transition: var(--transition-smooth);
  z-index: 998;
  box-shadow: 0 5px 20px rgba(37, 99, 235, 0.3);
  padding: 0;
}

.lang-toggle-btn i {
  font-size: 1.25rem;
}

.lang-toggle-btn #langText {
  font-size: 0.75rem;
  font-weight: 700;
  line-height: 1;
}

.lang-toggle-btn:hover {
  transform: translateY(-5px) scale(1.05);
  box-shadow: 0 8px 25px rgba(37, 99, 235, 0.4);
}

/* Adjust back-to-top position when language toggle is present */
.back-to-top {
  bottom: 100px; /* Move up to make room for language toggle */
}

@media (max-width: 768px) {
  .lang-toggle-btn {
    width: 55px;
    height: 55px;
    bottom: 20px;
    right: 20px;
  }

  .back-to-top {
    bottom: 85px;
    right: 20px;
  }
}

/* ========== Comprehensive Mobile Responsive Styles ========== */
@media (max-width: 768px) {
  /* Navbar Mobile */
  .navbar {
    padding: 1rem 0;
  }

  .navbar-brand img {
    max-height: 40px;
  }

  .nav-link {
    padding: 0.75rem 1rem !important;
    margin: 0.25rem 0;
  }

  .btn-primary,
  .btn-outline-primary {
    padding: 0.625rem 1.5rem;
    font-size: 0.875rem;
  }

  /* Hero Section Mobile */
  .hero-section {
    padding: 80px 0 40px;
    min-height: auto;
  }

  .hero-content {
    text-align: center;
    margin-bottom: 2rem;
  }

  .hero-badge {
    font-size: 0.75rem;
    padding: 0.4rem 1rem;
  }

  .hero-title {
    font-size: 2rem;
    margin-bottom: 1rem;
  }

  .hero-subtitle {
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
  }

  .hero-cta {
    flex-direction: column;
    gap: 0.75rem;
    justify-content: center;
    align-items: center;
  }

  .hero-cta .btn {
    width: 100%;
    max-width: 300px;
    margin: 0 auto;
  }

  .hero-image {
    margin-top: 2rem;
  }

  .hero-image img {
    border-radius: 20px;
  }

  /* About Section Mobile */
  .about-content {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .about-text {
    order: 2;
  }

  .about-image {
    order: 1;
    margin-bottom: 2rem;
  }

  .about-image img {
    width: 100%;
    height: auto;
  }

  .about-image {
    overflow: visible;
  }

  .about-image .glass-card {
    position: relative !important;
    top: auto !important;
    bottom: auto !important;
    right: auto !important;
    left: auto !important;
    max-width: 100% !important;
    margin-top: 1.5rem;
    margin-bottom: 0 !important;
    transform: none !important;
    z-index: auto !important;
  }

  .about-stats {
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-top: 1.5rem;
  }

  .stat-item {
    padding: 1rem;
  }

  .stat-number {
    font-size: 1.5rem;
  }

  .stat-label {
    font-size: 0.75rem;
  }

  /* Section Headers Mobile */
  .section-header {
    margin-bottom: 2.5rem;
  }

  .section-title {
    font-size: 1.75rem;
  }

  .section-description {
    font-size: 1rem;
    line-height: 1.6;
  }

  /* Topics Section Mobile */
  .topics-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .topic-card {
    padding: 1.5rem;
  }

  .topic-icon {
    width: 50px;
    height: 50px;
    font-size: 1.5rem;
  }

  .topic-title {
    font-size: 1.125rem;
    margin-bottom: 0.75rem;
  }

  .topic-description {
    font-size: 0.875rem;
    line-height: 1.6;
  }

  /* Timeline Mobile */
  .timeline {
    padding: 1rem 0;
  }

  .timeline-item {
    margin-bottom: 3rem;
  }

  .timeline-content {
    padding: 1.5rem;
    margin-left: 5rem;
    margin-right: 0;
  }

  .timeline-title {
    font-size: 1.125rem;
    margin-bottom: 0.5rem;
  }

  .timeline-description {
    font-size: 0.875rem;
  }

  /* Speakers Section Mobile */
  .speakers-grid {
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 1.5rem;
  }

  .speaker-card {
    padding: 1.5rem;
  }

  .speaker-avatar {
    width: 100px;
    height: 100px;
    margin-bottom: 1rem;
  }

  .speaker-name {
    font-size: 1rem;
  }

  .speaker-title {
    font-size: 0.875rem;
  }

  .speaker-bio {
    font-size: 0.8rem;
  }

  /* CFP Section Mobile */
  .cfp-section {
    padding: 3rem 0;
  }

  .cfp-content {
    text-align: center;
  }

  .cfp-title {
    font-size: 1.75rem;
    margin-bottom: 1rem;
  }

  .cfp-description {
    font-size: 0.95rem;
    margin-bottom: 2rem;
  }

  .cfp-features {
    grid-template-columns: 1fr;
    gap: 1.5rem;
    margin-bottom: 2rem;
  }

  .cfp-feature {
    padding: 1.5rem;
  }

  .cfp-feature-icon {
    width: 50px;
    height: 50px;
    font-size: 1.5rem;
    margin-bottom: 1rem;
  }

  .cfp-feature-title {
    font-size: 1.125rem;
  }

  .cfp-feature-text {
    font-size: 0.875rem;
  }

  /* Contact & Registration Mobile */
  .registration-section .row {
    flex-direction: column-reverse;
  }

  .contact-info-wrapper {
    min-height: auto !important;
    padding: 1.5rem 0 !important;
    margin-bottom: 2rem;
  }

  .contact-info-wrapper h3 {
    text-align: center;
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
  }

  .contact-info-wrapper .d-flex.flex-column {
    gap: 1.5rem !important;
  }

  .contact-info-wrapper .d-flex.align-items-start {
    flex-direction: column;
    align-items: center !important;
    text-align: center;
    gap: 0.75rem !important;
  }

  .contact-info-wrapper .d-flex.align-items-start > div:first-child {
    width: 45px !important;
    height: 45px !important;
    font-size: 1.1rem !important;
  }

  .contact-info-wrapper h5 {
    font-size: 0.8rem !important;
    margin-bottom: 0.5rem !important;
  }

  .contact-info-wrapper p {
    font-size: 0.95rem !important;
    line-height: 1.5 !important;
  }

  .registration-card {
    padding: 1.5rem;
  }

  .registration-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
  }

  .form-group {
    margin-bottom: 1.25rem;
  }

  .form-input {
    padding: 12px 15px 12px 45px;
    font-size: 14px;
  }

  .form-label {
    font-size: 14px;
    left: 45px;
  }

  .input-icon {
    left: 12px;
    font-size: 16px;
  }

  .btn-submit {
    width: 100%;
    padding: 0.875rem 1.5rem;
  }

  /* Footer Mobile */
  .footer {
    padding: 3rem 0 1rem;
  }

  .footer-content {
    grid-template-columns: 1fr;
    gap: 2rem;
    text-align: center;
  }

  .footer-section h4 {
    font-size: 1.125rem;
    margin-bottom: 1rem;
  }

  .footer-links {
    list-style: none;
    padding: 0;
  }

  .footer-links li {
    margin-bottom: 0.5rem;
  }

  .footer-bottom {
    margin-top: 2rem;
    text-align: center;
  }

  .footer-bottom p {
    font-size: 0.875rem;
  }
}

/* Extra Small Devices (phones, 480px and down) */
@media (max-width: 480px) {
  .hero-title {
    font-size: 1.75rem;
  }

  .section-title {
    font-size: 1.5rem;
  }

  .countdown-circle-wrapper {
    width: 80px;
    height: 80px;
  }

  .progress-ring {
    width: 80px;
    height: 80px;
  }

  .countdown-number {
    font-size: 1.25rem;
  }

  .countdown-label {
    font-size: 0.6rem;
  }

  .about-stats {
    grid-template-columns: 1fr;
  }

  .timeline-content {
    padding: 1.25rem;
    margin-left: 4rem;
  }

  .timeline-date {
    width: 60px;
    height: 60px;
    font-size: 0.7rem;
  }

  .speakers-grid {
    grid-template-columns: 1fr;
  }

  .topic-card,
  .speaker-card,
  .cfp-feature {
    padding: 1.25rem;
  }

  .registration-card {
    padding: 1.25rem;
  }
}