/* CSS Reset */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Segoe UI', Arial, sans-serif;
  background: #f0f4f8;
  min-height: 100vh;
  color: #222;
  position: relative;
}
.hero-bg {
  position: relative;
  width: 100vw;
  left: 50%;
  right: 50%;
  margin-left: -50vw;
  margin-right: -50vw;
  min-height: 320px;
  background: url('https://images.unsplash.com/photo-1461749280684-dccba630e2f6?auto=format&fit=crop&w=1200&q=80') center/cover no-repeat;
  z-index: 1;
}
.hero-overlay {
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: linear-gradient(120deg, #8e44adcc 0%, #3498dbcc 100%);
  opacity: 0.85;
  z-index: 2;
}
.main-header {
  position: relative;
  z-index: 3;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 48px 0 32px 0;
  text-align: center;
}
.logo {
  width: 72px;
  height: 72px;
  border-radius: 16px;
  box-shadow: 0 4px 24px #2222;
  margin-bottom: 18px;
  background: #fff;
}
.main-title {
  font-size: 2.8rem;
  color: #fff;
  letter-spacing: 2px;
  text-shadow: 0 4px 24px #2226;
  font-weight: 800;
  margin-bottom: 10px;
  animation: fadeInDown 1s cubic-bezier(.77,0,.18,1) 0.1s both;
}
.main-tagline {
  color:#fdfdfd;
  font-size: 1.25rem;
  margin-bottom: 0;
  text-shadow: 0 2px 8px #2224;
  animation: fadeInDown 1s cubic-bezier(.77,0,.18,1) 0.2s both;
}
main {
  max-width: 900px;
  margin: -80px auto 0 auto;
  background: #fff;
  border-radius: 18px;
  box-shadow: 0 8px 32px #8e44ad22;
  padding: 48px 24px 32px 24px;
  position: relative;
  z-index: 10;
}
.section-title {
  font-size: 1.7rem;
  color: #8e44ad;
  margin-bottom: 18px;
  letter-spacing: 1px;
  text-shadow: 0 2px 8px #8e44ad22;
  animation: fadeInDown 1s cubic-bezier(.77,0,.18,1) 0.2s both;
  text-align: center;
}
.file-list,
.challenge-list {
  list-style: none;
  padding: 0;
  margin-top: 24px;
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  justify-content: center;
}
.file-list li,
.challenge-list li {
  margin: 0;
  animation: fadeInUp 0.7s cubic-bezier(.77,0,.18,1) both;
}
.file-list a,
.challenge-list a {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 18px 28px;
  background: linear-gradient(90deg, #fff 70%, #eaf7ff 100%);
  color: #2c3e50;
  text-decoration: none;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(52, 152, 219, 0.08);
  font-size: 1.12rem;
  font-weight: 600;
  transition: background 0.3s, color 0.3s, transform 0.2s, box-shadow 0.2s;
  position: relative;
  overflow: hidden;
  min-width: 220px;
  min-height: 56px;
}
.file-list a::before {
  content: '\2192';
  color: #3498db;
  font-size: 1.2rem;
  margin-right: 10px;
  opacity: 0;
  transform: translateX(-10px);
  transition: opacity 0.3s, transform 0.3s;
}
.file-list a:hover::before {
  opacity: 1;
  transform: translateX(0);
}
.file-list a:hover,
.challenge-list a:hover {
  background: linear-gradient(90deg, #3498db 60%, #8e44ad 100%);
  color: #fff;
  transform: translateY(-4px) scale(1.04);
  box-shadow: 0 8px 32px #3498db33;
}
.file-list a:active,
.challenge-list a:active {
  transform: scale(0.98);
}
.challenge-list a {
  background: linear-gradient(90deg, #f8f9fa 70%, #eaf7ff 100%);
  border-left: 4px solid #28a745;
  color: #222;
  min-width: 220px;
  min-height: 56px;
}
.challenge-list a:hover {
  background: linear-gradient(90deg, #28a745 60%, #3498db 100%);
  color: #fff;
  border-left: 4px solid #3498db;
}
.challenge-coming-soon {
  opacity: 0.7;
  pointer-events: none;
  font-style: italic;
}
.section-divider {
  margin: 48px 0 32px 0;
  border: none;
  border-top: 2px dashed #8e44ad33;
  height: 0;
  width: 100%;
  animation: fadeIn 1.2s cubic-bezier(.77,0,.18,1) 0.3s both;
}
.main-footer {
  text-align: center;
  margin-top: 48px;
  color: #888;
  font-size: 1rem;
  padding-bottom: 16px;
}
.heart {
  color: #e74c3c;
  font-size: 1.2em;
  vertical-align: middle;
  animation: pulse 1.2s infinite alternate;
}
@keyframes pulse {
  from { transform: scale(1); }
  to { transform: scale(1.15); }
}
@media (max-width: 900px) {
  main {
    max-width: 98vw;
    padding: 24px 2vw 24px 2vw;
  }
  .file-list a, .challenge-list a {
    font-size: 1rem;
    padding: 14px 10px;
    min-width: 160px;
    min-height: 44px;
  }
}
@media (max-width: 700px) {
  .main-header {
    padding: 32px 0 18px 0;
  }
  .main-title {
    font-size: 2rem;
  }
  .section-title {
    font-size: 1.2rem;
  }
  main {
    margin-top: -40px;
    padding: 12px 2vw 12px 2vw;
  }
  .file-list, .challenge-list {
    gap: 10px;
  }
}
:focus {
  outline: 2px solid #3498db;
  outline-offset: 2px;
}
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-30px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}