* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Pretendard', sans-serif;
  background: linear-gradient(180deg, #f5f9ff 0%, #ffffff 100%);
  color: #1f2937;
  min-height: 100vh;
}

body.dark-mode {
  background: radial-gradient(1200px 800px at 20% -10%, rgba(37, 99, 235, 0.18) 0%, transparent 55%),
    radial-gradient(900px 640px at 95% 20%, rgba(14, 165, 233, 0.16) 0%, transparent 60%),
    #0b1120;
  color: #e2e8f0;
}

.main-content {
  max-width: 1080px;
  margin: 110px auto 80px;
  padding: 0 24px 60px;
  display: flex;
  flex-direction: column;
  gap: 80px;
}

.hero {
  text-align: left;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 14px;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.2px;
  color: #2563eb;
  background: rgba(37, 99, 235, 0.12);
  border-radius: 999px;
  margin-bottom: 20px;
}

body.dark-mode .hero-tag {
  color: #93c5fd;
  background: rgba(59, 130, 246, 0.18);
}

.hero h1 {
  margin: 0 0 16px;
  font-size: 40px;
  line-height: 1.25;
  color: #0f172a;
}

body.dark-mode .hero h1 {
  color: #f8fafc;
}

.hero p {
  margin: 0 0 32px;
  font-size: 18px;
  color: #4b5563;
  max-width: 640px;
}

body.dark-mode .hero p {
  color: #cbd5f5;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 36px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 28px;
  border-radius: 12px;
  font-size: 16px;
  font-weight: 700;
  cursor: pointer;
  border: none;
  transition: transform 0.18s ease, box-shadow 0.18s ease, background 0.18s ease, color 0.18s ease;
}

.btn-primary {
  background: linear-gradient(135deg, #3daeFA 0%, #2563eb 100%);
  color: #fff;
  box-shadow: 0 10px 24px rgba(61, 174, 250, 0.28);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 14px 30px rgba(61, 174, 250, 0.32);
}

.btn-secondary {
  background: #fff;
  color: #2563eb;
  border: 1.5px solid rgba(37, 99, 235, 0.25);
  box-shadow: 0 8px 20px rgba(37, 99, 235, 0.08);
}

body.dark-mode .btn-secondary {
  background: rgba(15, 23, 42, 0.6);
  color: #bfdbfe;
  border-color: rgba(148, 163, 184, 0.35);
  box-shadow: 0 10px 24px rgba(8, 15, 35, 0.55);
}

.btn-secondary:hover {
  transform: translateY(-2px);
  background: rgba(37, 99, 235, 0.06);
}

.hero-tier-ribbon {
  display: flex;
  gap: 16px;
  overflow-x: auto;
  padding-bottom: 6px;
}

.hero-tier {
  min-width: 150px;
  padding: 16px 18px;
  border-radius: 16px;
  background: #fff;
  border: 1px solid rgba(219, 234, 254, 0.9);
  box-shadow: 0 4px 18px rgba(37, 99, 235, 0.08);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  text-align: center;
}

.hero-tier img {
  width: 42px;
  height: 42px;
  object-fit: contain;
}

.hero-tier span {
  font-size: 15px;
  font-weight: 700;
  color: #111827;
}

.hero-tier small {
  font-size: 13px;
  color: #6b7280;
}

.hero-tier-top {
  border: 1px solid rgba(255, 112, 112, 0.36);
  box-shadow: 0 8px 24px rgba(255, 112, 112, 0.22);
}

body.dark-mode .hero-tier {
  background: rgba(15, 23, 42, 0.72);
  border-color: rgba(148, 163, 184, 0.2);
  box-shadow: 0 16px 32px rgba(8, 15, 35, 0.55);
}

body.dark-mode .hero-tier span {
  color: #f8fafc;
}

body.dark-mode .hero-tier small {
  color: #cbd5f5;
}

body.dark-mode .hero-tier-top {
  border-color: rgba(248, 113, 113, 0.4);
  box-shadow: 0 16px 34px rgba(248, 113, 113, 0.25);
}

.tier-section .section-head,
.workflow-section .section-head {
  max-width: 720px;
  margin-bottom: 32px;
}

.section-head h2 {
  margin: 0 0 12px;
  font-size: 30px;
  color: #0f172a;
}

body.dark-mode .section-head h2 {
  color: #f8fafc;
}

.section-head p {
  margin: 0;
  font-size: 17px;
  color: #4b5563;
  line-height: 1.5;
}

body.dark-mode .section-head p {
  color: #cbd5f5;
}

.tier-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 22px;
}

.tier-card {
  background: #fff;
  border-radius: 20px;
  border: 1.5px solid rgba(219, 234, 254, 0.9);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.08);
  padding: 28px 24px;
  display: flex;
  gap: 20px;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.tier-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 14px 26px rgba(37, 99, 235, 0.14);
}

.tier-card img {
  width: 60px;
  height: 60px;
  object-fit: contain;
  flex-shrink: 0;
}

.tier-card-body h3 {
  margin: 0 0 8px;
  font-size: 20px;
  color: #0f172a;
}

.tier-range {
  display: inline-block;
  margin-bottom: 10px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 700;
  color: #2563eb;
  background: rgba(37, 99, 235, 0.12);
  border-radius: 999px;
}

.tier-card-body p {
  margin: 0;
  font-size: 15px;
  color: #4b5563;
  line-height: 1.55;
}

.tier-card.tier-ruby {
  border: 1.5px solid rgba(255, 112, 112, 0.4);
  box-shadow: 0 12px 28px rgba(255, 112, 112, 0.18);
}

.tier-card.tier-ruby .tier-range {
  color: #e11d48;
  background: rgba(225, 29, 72, 0.12);
}

body.dark-mode .tier-card {
  background: rgba(15, 23, 42, 0.78);
  border-color: rgba(148, 163, 184, 0.18);
  box-shadow: 0 20px 38px rgba(8, 15, 35, 0.6);
}

body.dark-mode .tier-card-body h3 {
  color: #f8fafc;
}

body.dark-mode .tier-range {
  color: #93c5fd;
  background: rgba(59, 130, 246, 0.18);
}

body.dark-mode .tier-card-body p {
  color: #cbd5f5;
}

body.dark-mode .tier-card.tier-ruby {
  border-color: rgba(244, 114, 182, 0.4);
  box-shadow: 0 22px 40px rgba(190, 18, 60, 0.35);
}

.workflow-section {
  display: flex;
  gap: 56px;
  align-items: stretch;
}

.workflow-content {
  flex: 1 1 55%;
}

.workflow-steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 18px;
  margin-bottom: 28px;
}

.workflow-step {
  background: #fff;
  border-radius: 18px;
  border: 1px solid rgba(219, 234, 254, 0.9);
  padding: 20px 22px;
  box-shadow: 0 8px 20px rgba(37, 99, 235, 0.1);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.workflow-step:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 26px rgba(37, 99, 235, 0.16);
}

.step-number {
  width: 36px;
  height: 36px;
  border-radius: 12px;
  background: linear-gradient(135deg, #3daeFA, #2563eb);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  margin-bottom: 14px;
  box-shadow: 0 6px 14px rgba(61, 174, 250, 0.3);
}

.workflow-step h3 {
  margin: 0 0 10px;
  font-size: 17px;
  color: #0f172a;
}

.workflow-step p {
  margin: 0;
  font-size: 14px;
  color: #4b5563;
  line-height: 1.5;
}

body.dark-mode .workflow-step {
  background: rgba(15, 23, 42, 0.78);
  border-color: rgba(148, 163, 184, 0.22);
  box-shadow: 0 20px 40px rgba(8, 15, 35, 0.55);
}

body.dark-mode .workflow-step h3 {
  color: #f8fafc;
}

body.dark-mode .workflow-step p {
  color: #cbd5f5;
}

.workflow-benefits {
  margin: 0;
  padding-left: 18px;
  color: #374151;
  font-size: 15px;
  line-height: 1.7;
}

.workflow-benefits li + li {
  margin-top: 6px;
}

body.dark-mode .workflow-benefits {
  color: #cbd5f5;
}

.workflow-preview {
  flex: 1 1 45%;
  display: flex;
  justify-content: center;
  align-items: center;
}

.problem-preview {
  width: 100%;
  max-width: 420px;
  background: linear-gradient(140deg, rgba(219, 234, 254, 0.9), rgba(255, 225, 231, 0.95));
  border-radius: 28px;
  padding: 28px;
  box-shadow: 0 20px 40px rgba(37, 99, 235, 0.18);
  border: 1px solid rgba(255, 255, 255, 0.6);
}

body.dark-mode .problem-preview {
  background: linear-gradient(140deg, rgba(30, 58, 138, 0.9), rgba(91, 33, 182, 0.85));
  border-color: rgba(148, 163, 184, 0.18);
  box-shadow: 0 28px 46px rgba(8, 15, 35, 0.7);
}

.preview-header h3 {
  margin: 0;
  font-size: 24px;
  color: #0f172a;
}

body.dark-mode .preview-header h3 {
  color: #f8fafc;
}

.preview-header p {
  margin: 8px 0 24px;
  font-size: 14px;
  color: #4b5563;
  line-height: 1.5;
}

body.dark-mode .preview-header p {
  color: #cbd5f5;
}

.preview-search {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.search-bar,
.difficulty-filter {
  flex: 1;
  min-width: 160px;
  background: rgba(255, 255, 255, 0.72);
  border-radius: 16px;
  padding: 12px 16px;
  font-size: 14px;
  color: #6b7280;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.6);
}

body.dark-mode .search-bar,
body.dark-mode .difficulty-filter {
  background: rgba(15, 23, 42, 0.65);
  color: #cbd5f5;
  box-shadow: inset 0 1px 0 rgba(148, 163, 184, 0.2);
}

.difficulty-filter {
  flex: 0 0 auto;
  padding-right: 46px;
  position: relative;
}

.difficulty-filter::after {
  content: '▾';
  position: absolute;
  right: 18px;
  top: 50%;
  transform: translateY(-50%);
  color: #9ca3af;
  font-size: 12px;
}

.preview-card {
  background: rgba(255, 255, 255, 0.9);
  border-radius: 20px;
  padding: 22px;
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.8);
}

body.dark-mode .preview-card {
  background: rgba(15, 23, 42, 0.85);
  border-color: rgba(148, 163, 184, 0.18);
  box-shadow: 0 20px 36px rgba(8, 15, 35, 0.65);
}

.preview-card-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 12px;
  gap: 12px;
}

.preview-title-block {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.preview-id {
  font-size: 12px;
  font-weight: 600;
  color: #9ca3af;
}

.preview-title {
  font-size: 18px;
  font-weight: 700;
  color: #111827;
}

body.dark-mode .preview-title {
  color: #f8fafc;
}

.preview-badge {
  display: inline-flex;
  align-items: center;
  padding: 6px 14px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.5px;
  color: #ef4444;
  background: rgba(239, 68, 68, 0.18);
  border-radius: 999px;
  text-transform: uppercase;
  box-shadow: 0 6px 14px rgba(239, 68, 68, 0.18);
}

body.dark-mode .preview-badge {
  color: #fecaca;
  background: rgba(248, 113, 113, 0.24);
  box-shadow: 0 10px 20px rgba(190, 18, 60, 0.38);
}

.preview-desc {
  margin: 0 0 18px;
  font-size: 14px;
  color: #4b5563;
  line-height: 1.6;
}

body.dark-mode .preview-desc {
  color: #cbd5f5;
}

.preview-tags {
  display: flex;
  gap: 10px;
}

.preview-tags .tag {
  padding: 6px 12px;
  font-size: 12px;
  color: #2563eb;
  background: rgba(37, 99, 235, 0.14);
  border-radius: 999px;
  font-weight: 600;
}

body.dark-mode .preview-tags .tag {
  color: #93c5fd;
  background: rgba(59, 130, 246, 0.22);
}

@media (max-width: 1024px) {
  .main-content {
    margin-top: 100px;
    gap: 64px;
  }

  .workflow-section {
    flex-direction: column;
  }

  .workflow-preview {
    order: -1;
  }

  .workflow-content,
  .workflow-preview {
    flex: 1 1 auto;
  }
}

@media (max-width: 720px) {
  .hero h1 {
    font-size: 32px;
  }

  .hero p {
    font-size: 16px;
  }

  .hero-tier-ribbon {
    gap: 12px;
  }

  .tier-card {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .tier-card-body p {
    font-size: 14px;
  }
}

@media (max-width: 540px) {
  .main-content {
    padding: 0 18px 40px;
  }

  .btn {
    width: 100%;
  }

  .hero-actions {
    flex-direction: column;
  }

  .preview-search {
    flex-direction: column;
  }

  .difficulty-filter {
    width: 100%;
  }
}