:root {
  --esn-cyan: #00a3e0;
  --esn-magenta: #ec008c;
  --esn-green: #7ac143;
  --esn-orange: #f7941d;
  --esn-dark-blue: #1b3a57;
  --esn-white: #ffffff;
  --esn-gray-50: #f6f8fa;
  --esn-gray-100: #eef2f5;
  --esn-gray-200: #d7e0e8;
  --esn-gray-700: #4b5b6a;
  --esn-shadow: 0 6px 20px rgba(27, 58, 87, 0.12);
  --radius-lg: 16px;
  --radius-md: 12px;
  --container: 1100px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Lato", "Helvetica Neue", Arial, sans-serif;
  color: var(--esn-dark-blue);
  background: var(--esn-gray-50);
  line-height: 1.6;
}

h1,
h2,
h3,
h4 {
  font-family: "Kelson Sans", "Avenir Next", "Segoe UI", Arial, sans-serif;
  margin: 0 0 0.6rem;
  line-height: 1.2;
}

p {
  margin: 0 0 1rem;
  color: var(--esn-gray-700);
}

a {
  color: inherit;
  text-decoration: none;
}

.container {
  width: min(100% - 2rem, var(--container));
  margin: 0 auto;
}

.section {
  padding: 3.5rem 0;
}

.section-title {
  font-size: clamp(1.6rem, 2.3vw, 2.3rem);
}

.card {
  background: var(--esn-white);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--esn-shadow);
  border: 1px solid var(--esn-gray-100);
}

.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.chip {
  padding: 0.5rem 0.9rem;
  border-radius: 999px;
  background: var(--esn-white);
  border: 1px solid var(--esn-gray-200);
  font-size: 0.9rem;
  font-weight: 600;
}

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-top: 1rem;
}

.agenda-controls {
  margin-bottom: 1rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0.7rem 1.2rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  border: 1px solid transparent;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  box-shadow: none;
}

.icon-button {
  gap: 0.4rem;
  padding: 0.3rem 1.5rem;
  min-width: 44px;
}

.icon-calendar {
  width: 22px;
  height: 22px;
  stroke: var(--esn-dark-blue);
  stroke-width: 1.6;
  fill: none;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  padding: 0.6rem 1rem;
  background: var(--esn-cyan);
  color: var(--esn-white);
  font-weight: 600;
  border-radius: var(--radius-md);
  z-index: 1000;
  transition: top 0.2s ease;
}
.skip-link:focus {
  top: 1rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.btn:hover,
.btn:focus-visible {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--esn-cyan);
  color: var(--esn-white);
}

.btn-secondary {
  background: var(--esn-white);
  border-color: var(--esn-gray-200);
  color: var(--esn-dark-blue);
}

.btn-disabled {
  opacity: 0.7;
  cursor: not-allowed;
}

/* Navigation */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--esn-white);
  border-bottom: 1px solid var(--esn-gray-100);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.8rem 0;
  gap: 1rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  font-weight: 700;
  min-height: 44px;
}

.logo-wrap {
  width: 52px;
  height: 52px;
  border-radius: 12px;
  display: grid;
  place-items: center;
  background: var(--esn-white);
  padding: 6px; /* safe zone placeholder */
  border: 1px solid var(--esn-gray-200);
}

.logo-img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.nav-toggle {
  min-height: 44px;
  min-width: 44px;
  border-radius: 12px;
  border: 1px solid var(--esn-gray-200);
  background: var(--esn-white);
  font-weight: 700;
  display: grid;
  place-items: center;
  padding: 0;
}

.hamburger {
  display: grid;
  gap: 4px;
}

.hamburger .bar {
  width: 20px;
  height: 2px;
  background: var(--esn-dark-blue);
  border-radius: 999px;
}

.nav-links {
  display: none;
  flex-direction: column;
  gap: 0.6rem;
  padding: 0.6rem 0 1rem;
}

.nav-links a {
  min-height: 44px;
  display: flex;
  align-items: center;
  padding: 0 0.6rem;
  border-radius: 12px;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  background: var(--esn-gray-50);
}

.nav-links.is-open {
  display: flex;
}

/* Hero */
.hero {
  background: linear-gradient(120deg, rgba(0, 163, 224, 0.15), rgba(236, 0, 140, 0.08)),
    url("background_hero_picture.png");
  background-size: cover;
  background-position: center;
  padding: 4.5rem 0 3.5rem;
}

.hero-card {
  max-width: 680px;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(6px);
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3rem);
}

.hero-subtitle {
  font-size: 1.1rem;
}

/* Grids */
.grid {
  display: grid;
  gap: 1.4rem;
}

/* Accordions */
details {
  border-radius: var(--radius-md);
  border: 1px solid var(--esn-gray-200);
  background: var(--esn-white);
  padding: 0.8rem 1rem;
}

details + details {
  margin-top: 0.8rem;
}

summary {
  list-style: none;
  cursor: pointer;
  font-weight: 600;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  content: "+";
  font-size: 1.2rem;
  color: var(--esn-cyan);
}

details[open] summary::after {
  content: "–";
}

.accordion-content {
  padding: 0.6rem 0 0.2rem;
  color: var(--esn-gray-700);
}

/* Agenda calendar blocks */
.agenda-grid {
  display: grid;
  gap: 0.8rem;
  margin-top: 0.6rem;
}

.agenda-calendar {
  display: none;
  gap: 1rem;
  margin-top: 1.5rem;
  grid-template-columns: repeat(5, minmax(0, 1fr));
}

.agenda-day {
  background: var(--esn-white);
  border-radius: var(--radius-lg);
  border: 1px solid var(--esn-gray-100);
  box-shadow: var(--esn-shadow);
  padding: 1rem;
  display: grid;
  gap: 0.7rem;
}

.agenda-day-title {
  text-align: center;
  font-weight: 700;
  padding: 0.6rem 0.8rem;
  border-radius: 12px;
  background: rgba(247, 148, 29, 0.2);
  border: 1px solid rgba(247, 148, 29, 0.35);
}

.agenda-event {
  text-align: center;
  font-weight: 600;
  padding: 0.6rem 0.7rem;
  border-radius: 10px;
  background: var(--esn-gray-50);
  border: 1px solid var(--esn-gray-200);
  display: grid;
  gap: 0.2rem;
}

.agenda-event .event-time {
  font-size: 0.85rem;
  font-weight: 400;
  color: var(--esn-gray-700);
}

.event-tall {
  min-height: 140px;
  display: grid;
  align-content: center;
}

.event-cyan {
  border-left: 4px solid var(--esn-cyan);
}

.event-magenta {
  border-left: 4px solid var(--esn-magenta);
}

.event-green {
  border-left: 4px solid var(--esn-green);
}

.event-orange {
  border-left: 4px solid var(--esn-orange);
}

.event-blue {
  border-left: 4px solid var(--esn-dark-blue);
}

.agenda-accordion {
  display: block;
}

.time-block {
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: 0.8rem;
  align-items: start;
  padding: 0.9rem 1rem;
  border-radius: var(--radius-md);
  background: var(--esn-gray-50);
  border: 1px solid var(--esn-gray-200);
}

.time-block .time {
  font-weight: 700;
  color: var(--esn-dark-blue);
  font-size: 0.95rem;
}

.time-block .session {
  color: var(--esn-dark-blue);
  font-weight: 600;
}

.time-block .meta {
  font-size: 0.9rem;
  color: var(--esn-gray-700);
}

.block-cyan {
  border-left: 6px solid var(--esn-cyan);
}

.block-magenta {
  border-left: 6px solid var(--esn-magenta);
}

.block-green {
  border-left: 6px solid var(--esn-green);
}

.block-orange {
  border-left: 6px solid var(--esn-orange);
}

/* Cards */
.card-header {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  font-weight: 700;
}

.color-dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

.dot-cyan {
  background: var(--esn-cyan);
}

.dot-magenta {
  background: var(--esn-magenta);
}

.dot-green {
  background: var(--esn-green);
}

.dot-orange {
  background: var(--esn-orange);
}

.doc-card a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 44px;
  padding: 0.4rem 0;
  color: var(--esn-cyan);
  font-weight: 600;
}

.map-embed {
  border-radius: var(--radius-md);
  border: 1px dashed var(--esn-gray-200);
  background: var(--esn-gray-50);
  padding: 0.8rem;
}

.map-embed iframe {
  width: 100%;
  height: 220px;
  border: 0;
  border-radius: 12px;
  background: var(--esn-white);
}

.map-note {
  margin: 0.7rem 0 0;
  font-size: 0.9rem;
  color: var(--esn-gray-700);
}

.map-note span {
  font-weight: 700;
}

.campus-map {
  margin-top: 1rem;
}

.campus-map-body {
  padding: 0.6rem 0 0.2rem;
}

.campus-map img {
  width: 100%;
  height: auto;
  border-radius: var(--radius-md);
  border: 1px solid var(--esn-gray-200);
  display: block;
}

.sponsor-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
}

.sponsor-heading {
  margin: 1.2rem 0 0.6rem;
}

.social-heading {
  margin: 0 0 0.6rem;
}

.sponsor-logo {
  border: 1px dashed var(--esn-gray-200);
  border-radius: var(--radius-md);
  min-height: 64px;
  display: grid;
  place-items: center;
  color: var(--esn-gray-700);
  background: var(--esn-gray-50);
  font-size: 0.9rem;
  text-align: center;
  padding: 0.4rem;
}

@media (min-width: 768px) {
  .sponsor-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.footer {
  background: var(--esn-dark-blue);
  color: var(--esn-white);
  padding: 2.5rem 0;
}

.footer p {
  color: rgba(255, 255, 255, 0.7);
}

@media (min-width: 768px) {
  .nav-toggle {
    display: none;
  }

  .nav-links {
    display: flex;
    flex-direction: row;
    padding: 0;
  }

  .hero-card {
    padding: 2.5rem;
  }

  .grid.two {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .grid.three {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .agenda-grid {
    gap: 1rem;
  }
}

@media (min-width: 1024px) {
  .agenda-calendar {
    display: none;
  }
}

@media (min-width: 1024px) {
  .section {
    padding: 4.5rem 0;
  }

  .hero {
    padding: 5.5rem 0 4.5rem;
  }
}