* {
  box-sizing: border-box;
}

body {
  font-family: -apple-system, "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
  background: #0b0d12;
  color: #e5e7eb;
  margin: 0;
  padding: 0 24px;
  line-height: 1.7;
}

.container {
  max-width: 720px;
  margin: 0 auto 32px;
  text-align: center;
}

h1 {
  font-size: 32px;
  font-weight: 800;
  margin-bottom: 8px;
}

.hint {
  font-size: 14px;
  color: #9ca3af;
  margin: 6px 0;
}

.link {
  color: #60a5fa;
  text-decoration: underline;
  cursor: pointer;
}

.level-select {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 10px;
  margin: 24px 0;
}

.level-btn {
  background: #12141a;
  border: 1px solid #262a33;
  border-radius: 10px;
  padding: 14px;
  text-align: left;
  cursor: pointer;
  color: #e5e7eb;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.level-btn strong {
  font-size: 15px;
}

.level-btn span {
  font-size: 12px;
  color: #9ca3af;
}

.level-btn.active {
  border-color: #60a5fa;
  box-shadow: 0 0 0 1px #60a5fa inset;
}

.drop-zone {
  background: #12141a;
  border: 2px dashed #2b2f38;
  border-radius: 14px;
  padding: 64px 24px;
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.drop-zone.dragover {
  border-color: #60a5fa;
  background: #161a22;
}

.drop-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto 16px;
  border-radius: 12px;
  background: #1c2028;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  color: #9ca3af;
}

.drop-title {
  font-size: 17px;
  font-weight: 600;
  margin: 0 0 6px;
}

.progress-wrap {
  margin-top: 20px;
}

.progress-bar {
  width: 100%;
  height: 8px;
  border-radius: 4px;
  background: #1c2028;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  width: 0%;
  background: #60a5fa;
  transition: width 0.2s ease;
}

.result-card {
  margin-top: 20px;
  background: #12141a;
  border: 1px solid #262a33;
  border-radius: 14px;
  padding: 24px;
}

.result-title {
  font-size: 18px;
  font-weight: 700;
  margin: 0 0 6px;
}

.result-detail {
  font-size: 14px;
  color: #9ca3af;
  margin: 0 0 16px;
}

.result-note {
  font-size: 12px;
  color: #f59e0b;
  margin: -8px 0 16px;
}

.btn-primary {
  background: #2563eb;
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 12px 20px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  margin-right: 8px;
}

.btn-secondary {
  background: transparent;
  color: #9ca3af;
  border: 1px solid #262a33;
  border-radius: 8px;
  padding: 12px 20px;
  font-size: 14px;
  cursor: pointer;
}

.error-msg {
  color: #f87171;
  font-size: 13px;
  min-height: 18px;
  margin-top: 12px;
}

a {
  color: #60a5fa;
}

.site-header {
  max-width: 720px;
  margin: 0 auto;
  padding: 18px 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px 16px;
  border-bottom: 1px solid #1c2028;
}

.site-header .brand {
  color: #e5e7eb;
  font-weight: 700;
  text-decoration: none;
}

.site-header nav {
  display: flex;
  gap: 16px;
  font-size: 14px;
}

.site-header nav a {
  color: #9ca3af;
  text-decoration: none;
}

.site-header nav a:hover {
  color: #e5e7eb;
}

.container.tool {
  padding-top: 32px;
}

.lead {
  font-size: 15px;
  color: #9ca3af;
  margin: 6px 0 0;
}

.container.content {
  text-align: left;
  margin-top: 48px;
}

.content h2 {
  font-size: 20px;
  margin: 40px 0 12px;
  padding-top: 8px;
}

.content h3 {
  font-size: 15px;
  margin: 0 0 6px;
}

.content p,
.content li {
  font-size: 15px;
  color: #cbd5e1;
}

.content ul,
.content ol {
  padding-left: 22px;
}

.content li {
  margin-bottom: 6px;
}

.content.page h1 {
  margin-bottom: 16px;
}

.steps li {
  margin-bottom: 10px;
}

.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.spec {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  margin: 12px 0;
}

.spec th,
.spec td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid #1c2028;
  color: #cbd5e1;
}

.spec th {
  color: #9ca3af;
  font-weight: 600;
}

details {
  border-bottom: 1px solid #1c2028;
  padding: 12px 0;
}

details summary {
  cursor: pointer;
  font-weight: 600;
  color: #e5e7eb;
}

details p {
  margin: 10px 0 0;
}

.site-footer {
  max-width: 720px;
  margin: 56px auto 0;
  padding: 24px 0 40px;
  border-top: 1px solid #1c2028;
  text-align: center;
  font-size: 14px;
}

.site-footer a {
  color: #9ca3af;
}

@media (max-width: 600px) {
  .level-select {
    grid-template-columns: 1fr;
  }
  .two-col {
    grid-template-columns: 1fr;
  }
  h1 {
    font-size: 26px;
  }
}