body {
  margin: 0;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: #ffffff;
  color: #111827;
  line-height: 1.6;
  font-size: 16px;
}

pre,
code {
  font-family: "Fira Code", monospace;
  line-height: normal;
}

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 310px;
  height: 100vh;
  background: linear-gradient(180deg, #ffffff 0%, #f3f4f6 100%);
  border-right: 1px solid #e5e7eb;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-sizing: border-box;
  font-family: "Inter", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

.sidebar-header {
  padding: 0;
  border-bottom: 1px solid #e5e7eb;
  background-color: #ffffff;
}

.cp-handbook-link {
  display: flex;
  align-items: center;
  width: 100%;
  box-sizing: border-box;
  padding: 14px 16px;
  font-weight: 600;
  font-size: 16px;
  text-decoration: none;
  color: #1f2937;
  background-color: #fcf8f2;
  border-radius: 0;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.cp-handbook-link:hover {
  background-color: #faefd6;
  color: #1e3a8a;
}

.cp-icon {
  width: 22px;
  height: 22px;
  margin-right: 8px;
  color: #2563eb;
  flex-shrink: 0;
}

.sidebar-search {
  position: sticky;
  padding: 12px 16px;
  background: linear-gradient(180deg, #ffffff, #f9fafb);
  border-bottom: 1px solid #e5e7eb;
  z-index: 15;
}

.sidebar-search .search-wrapper {
  display: flex;
  align-items: center;
  gap: 8px;
  background-color: #ffffff;
  border: 1px solid #d1d5db;
  border-radius: 10px;
  padding: 6px 10px;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.05);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.sidebar-search .search-wrapper:focus-within {
  border-color: #2563eb;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.18);
}

.sidebar-search input {
  flex: 1;
  border: none;
  outline: none;
  font-size: 14px;
  background: transparent;
  color: #111827;
}

.sidebar-search input::placeholder {
  color: #9ca3af;
}

#clearSearchBtn {
  background-color: #fee2e2;
  border: 1px solid #fecaca;
  color: #991b1b;
  border-radius: 6px;
  cursor: pointer;
  font-size: 13px;
  padding: 4px 8px;
  line-height: 1;
  transition: background-color 0.15s ease, transform 0.1s ease;
}

#clearSearchBtn:hover {
  background-color: #fecaca;
  transform: scale(1.05);
}

.phase-selector {
  padding: 16px;
  background: #ffffff;
  border-bottom: 1px solid #e5e7eb;
  position: sticky;
  top: 110px;
  z-index: 15;
}

.phase-selector select {
  width: 100%;
  padding: 11px 40px 11px 14px;
  font-size: 14px;
  font-weight: 600;
  color: #111827;
  background-color: #ffffff;
  border: 1px solid #cbd5e1;
  border-radius: 10px;
  outline: none;
  cursor: pointer;
  appearance: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease,
    background-color 0.2s ease;
  background-image: linear-gradient(45deg, transparent 50%, #6b7280 50%),
    linear-gradient(135deg, #6b7280 50%, transparent 50%);
  background-position: right 18px center, right 12px center;
  background-size: 6px 6px;
  background-repeat: no-repeat;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.05);
}

.phase-selector select:hover {
  background-color: #f9fafb;
  border-color: #9ca3af;
}

.phase-selector select:focus {
  border-color: #2563eb;
  background-color: #ffffff;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.18);
}

.sidebar-content {
  flex: 1 1 auto;
  overflow-y: auto;
  padding: 7px;
}

:root {
  --main-padding-top: 20px;
  --main-padding-right: 36px;
  --main-padding-bottom: 20px;
  --main-padding-left: 30px;
}

main {
  margin-left: 310px;
  padding: var(--main-padding-top) var(--main-padding-right)
    var(--main-padding-bottom) var(--main-padding-left);
  max-width: 1500px;
  background-color: #ffffff;
}

main > :first-child {
  margin-top: 0px;
}

main h1 {
  margin-top: 0px;
  margin-bottom: 12px;
}

main h2 {
  margin-top: 20px;
  margin-bottom: 10px;
}

main h3 {
  margin-top: 16px;
  margin-bottom: 8px;
}

main ul {
  margin: 0;
  padding-left: 25px;
}

main ul ul,
details .spoiler-content ul ul {
  list-style-type: disc;
}

main li {
  margin: 0;
  padding: 0;
  line-height: 1.6;
}

main a {
  color: #2563eb;
  text-decoration: none;
  font-weight: 500;
  transition: color 0.15s ease;
}

main a:hover {
  color: #1e40af;
}

main a:visited {
  color: #2563eb;
}

main ul li + li {
  margin-top: 4px;
}

.topic {
  margin-top: 8px;
}

.topic-title {
  font-weight: 600;
  font-size: 14px;
  padding: 10px 14px;
  cursor: pointer;
  color: #1f2937;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-radius: 8px;
  margin: 4px 10px;
  background-color: transparent;
  transition: background-color 0.15s ease, color 0.15s ease,
    box-shadow 0.15s ease;
}

.topic-title:hover {
  background-color: #eef2ff;
  color: #1e3a8a;
}

.topic-title::after {
  content: "▸";
  font-size: 16px;
  color: #6b7280;
  transition: transform 0.2s ease, color 0.15s ease;
}

.topic-title.open::after {
  content: "▾";
}

.topic-title.open.phase1 {
  background-color: #cce5ff;
  color: #004085;
}

.topic-title.open.phase2 {
  background-color: #d4edda;
  color: #155724;
}

.topic-title.open.phase3 {
  background-color: #f8d7da;
  color: #721c24;
}

.topic-title.open.phase1::after {
  color: #004085;
}
.topic-title.open.phase2::after {
  color: #155724;
}
.topic-title.open.phase3::after {
  color: #721c24;
}

.topic-body {
  background: #f9fafb;
  border-left: 3px solid #c7d2fe;
  margin: 4px 12px 6px 18px;
  border-radius: 0 8px 8px 0;
  padding: 6px 0;
}

.topic-link {
  display: block;
  padding: 7px 14px;
  margin: 2px 8px;
  font-family: "Inter", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 13.5px;
  font-weight: 500;
  letter-spacing: 0.1px;
  color: #374151;
  text-decoration: none;
  border-radius: 6px;
  transition: background-color 0.12s ease, color 0.12s ease,
    transform 0.12s ease;
}

.topic-link:hover {
  background-color: #eef2ff;
  color: #1e40af;
  transform: translateX(2px);
}

.topic-link.active {
  background-color: #2563eb;
  color: #ffffff;
  font-weight: 600;
}

.topic-link.active:hover {
  background-color: #2563eb;
  color: #ffffff;
  transform: none;
}

details {
  margin: 6px 0;
}

details > summary {
  cursor: pointer;
  font-weight: bold;
  padding: 6px 12px 6px 36px;
  background-color: #f3f4f6;
  border-radius: 4px 4px 0 0;
  margin-bottom: 0;
  list-style: none;
  display: list-item;
  position: relative;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

details > summary::before {
  content: "▸";
  position: absolute;
  left: 10px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 18px;
  color: #6b7280;
  transition: transform 0.2s ease, color 0.2s ease;
}

details[open] > summary::before {
  content: "▾";
  color: #2563eb;
}

details .spoiler-content {
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: #f9fafb;
  padding: 6px 12px;
  margin-top: 0px;
  margin-bottom: 6px;
  border-radius: 0 0 4px 4px;
}

details .spoiler-content ul {
  margin: 0px 0;
  padding-left: 25px;
}

details .spoiler-content li {
  margin: 0;
  padding: 0;
  line-height: 1.6;
}

details > pre {
  margin: 0;
  overflow-x: auto;
  font-family: "Fira Code", monospace;
  font-size: 14px;
  background-color: #f9fafb !important;
  border-radius: 0 0 4px 4px;
}

details > pre code {
  background-color: transparent !important;
  line-height: normal !important;
}

.page-info-container {
  text-align: left;
  margin-bottom: 12px;
}

.page-info {
  display: inline-block;
  text-align: left;
  font-weight: 600;
  font-size: 14px;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

.page-info .info-row {
  margin-bottom: 2px;
}

.page-info .level {
  padding: 2px 8px;
  border-radius: 4px;
}

.page-info .level.very-easy {
  background-color: #d4edda;
  color: #155724;
}

.page-info .level.easy {
  background-color: #fff3cd;
  color: #856404;
}

.page-info .level.medium {
  background-color: #ffe5b4;
  color: #8b5c00;
}

.page-info .level.hard {
  background-color: #f8d7da;
  color: #721c24;
}

.page-info .stars {
  color: #f59e0b;
  font-size: 16px;
  line-height: 1;
}

.info-table {
  width: 100%;
  border-collapse: collapse;
  border: 2px solid #d1d5db;
  margin: 16px 0;
  font-size: 14px;
  background-color: #f9fafb;
  border-radius: 8px;
  overflow: hidden;
}

.info-table th,
.info-table td {
  padding: 12px 16px;
  text-align: left;
  border: 1px solid #d1d5db;
}

.info-table thead {
  background-color: #e5e7eb;
}

.info-table th {
  font-weight: 600;
  color: #111827;
}

.info-table td {
  color: #374151;
  background-color: #ffffff;
}

.info-table th:first-child,
.info-table td:first-child {
  width: 150px;
  white-space: nowrap;
}

.info-table td .level {
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 4px;
  display: inline-block;
}

.info-table td .level.very-easy {
  background-color: #d4edda;
  color: #155724;
}

.info-table td .level.easy {
  background-color: #fff3cd;
  color: #856404;
}

.info-table td .level.medium {
  background-color: #ffe5b4;
  color: #8b5c00;
}

.info-table td .level.hard {
  background-color: #f8d7da;
  color: #721c24;
}

.info-table td .stars {
  font-size: 16px;
  line-height: 1;
  color: #f59e0b;
}

.info-table tr:hover td {
  background-color: #eef2ff;
}

summary[data-type="solution"] {
  background-color: #e6f4ea;
}

summary[data-type="code"] {
  background-color: #ddf2f7;
}

pre.sample-io {
  font-family: "JetBrains Mono", monospace;
  font-size: 15px;
  background-color: #f3f4f6;
  padding: 8px 12px;
  border-radius: 6px;
  border: 1px solid #d1d5db;
  overflow-x: auto;
  line-height: 1.5;
  margin: 6px 0;
  color: #111827;
}

.sample-block {
  position: relative;
  margin: 8px 0;
}

.copy-btn {
  background-color: #6b7280;
  color: #fff;
  border: none;
  border-radius: 4px;
  padding: 2px 8px;
  font-size: 12px;
  cursor: pointer;
  transition: background-color 0.15s ease;
  margin-left: 5px;
  vertical-align: middle;
}

.copy-btn:hover {
  background-color: #4b5563;
}

.spoiler-code {
  background-color: #f2f7fc !important;
}

details > summary[data-type="solution"] + .spoiler-content {
  background-color: #f4f9f6;
}

.solution-toggle-btn {
  margin-left: 10px;
  float: right;
  padding: 3px 12px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  border-radius: 6px;
  transition: all 0.2s ease;
  vertical-align: middle;
  background-color: #f8fafc;
  color: #475569;
  border: 1px solid #cbd5e1;
}

.solution-toggle-btn:hover {
  background-color: #f1f5f9;
  border-color: #94a3b8;
}

.solution-toggle-btn.active {
  background-color: #fff1f2;
  color: #be123c;
  border: 1px solid #fda4af;
}

.solution-toggle-btn.active:hover {
  background-color: #ffe4e6;
  border-color: #fb7185;
}

.practice-solution-container {
  margin-top: 12px;
  margin-bottom: 12px;
}