/* P-complete Compendium - Main Stylesheet */

/* Material Symbols baseline (required for ligature icon names) */
.material-symbols-outlined {
  font-family: "Material Symbols Outlined";
  font-weight: normal;
  font-style: normal;
  font-size: 1rem;
  display: inline-block;
  line-height: 1;
  letter-spacing: normal;
  text-transform: none;
  white-space: nowrap;
  word-wrap: normal;
  direction: ltr;
  font-feature-settings: "liga";
  -webkit-font-feature-settings: "liga";
  -webkit-font-smoothing: antialiased;
}

:root {
  --color-bg: #ffffff;
  --color-text: #1a1a1a;
  --color-text-muted: #666666;
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-accent: #059669;
  --color-border: #e5e7eb;
  --color-card-bg: #f9fafb;
  --color-p-complete: #059669;
  --color-p-hard: #dc2626;
  --color-open: #d97706;
  --color-header-bg: #1a1a1a;
  --color-header-text: #ffffff;
  --color-header-muted: rgba(255, 255, 255, 0.8);
  --color-header-button-bg: rgba(255, 255, 255, 0.08);
  --color-header-button-border: rgba(255, 255, 255, 0.25);
  --color-header-button-hover: rgba(255, 255, 255, 0.16);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --max-width: 1200px;
  --content-width: 800px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --radius-sm: 8px;
  --radius-md: 10px;
  --radius-lg: 12px;
  --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 10px 24px rgba(0, 0, 0, 0.12);
}

html[data-theme="dark"] {
  /* Monokai-inspired palette */
  --color-bg: #272822;
  --color-text: #f8f8f2;
  --color-text-muted: #cfcfc2;
  --color-primary: #66d9ef;
  --color-primary-dark: #50c7df;
  --color-accent: #a6e22e;
  --color-border: #49483e;
  --color-card-bg: #2f3129;
  --color-p-complete: #a6e22e;
  --color-p-hard: #ff6188;
  --color-open: #fd971f;
  --color-header-bg: #1e1f1c;
  --color-header-text: #f8f8f2;
  --color-header-muted: #d6d6cf;
  --color-header-button-bg: #3b3a32;
  --color-header-button-border: #6a6a5c;
  --color-header-button-hover: #4a4940;
  --shadow-sm: 0 6px 16px rgba(0, 0, 0, 0.45);
  --shadow-md: 0 12px 26px rgba(0, 0, 0, 0.42);
}

/* Reset */
*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
}

a {
  color: var(--color-primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Header */
.site-header {
  background: var(--color-header-bg);
  color: var(--color-header-text);
  padding: 0.85rem 0;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.nav-container.nav-home {
  justify-content: flex-end;
}

.nav-controls {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.site-title {
  color: var(--color-header-text);
  font-size: 1.25rem;
  font-weight: 600;
}

.site-title:hover {
  text-decoration: none;
  opacity: 0.9;
}

.nav-menu {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 1.5rem;
}

.nav-menu a {
  color: var(--color-header-muted);
  font-size: 0.92rem;
}

.nav-menu a:hover,
.nav-menu a.active {
  color: var(--color-header-text);
  text-decoration: none;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  background: var(--color-header-button-bg);
  color: var(--color-header-text);
  border: 1px solid var(--color-header-button-border);
  border-radius: 6px;
  padding: 0.35rem 0.55rem;
  font-size: 0.85rem;
  cursor: pointer;
}

.theme-toggle-icon {
  font-size: 1rem;
  line-height: 1;
}

.theme-toggle:hover {
  background: var(--color-header-button-hover);
}

.theme-toggle:focus-visible {
  outline: 2px solid #93c5fd;
  outline-offset: 2px;
}

/* Footer */
.site-footer {
  background: var(--color-card-bg);
  border-top: 1px solid var(--color-border);
  padding: 1.7rem 0;
  margin-top: 3.25rem;
}

.footer-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.86rem;
}

.footer-content p {
  margin: 0.5rem 0;
}

/* Content */
.single {
  max-width: var(--content-width);
  margin: 0 auto;
}

.single h1 {
  margin-top: 0;
}

/* Markdown code blocks */
pre,
code {
  font-family: var(--font-mono);
}

pre {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  padding: 0.85rem 1rem;
  overflow-x: auto;
  color: var(--color-text);
}

pre code {
  background: transparent;
  border: 0;
  padding: 0;
  color: inherit;
}

code {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 0.1rem 0.35rem;
  color: var(--color-text);
}

/* Hugo/Chroma may emit inline light backgrounds; force dark-friendly block in dark mode */
html[data-theme="dark"] .highlight pre {
  background: var(--color-card-bg) !important;
  border-color: var(--color-border);
  color: var(--color-text) !important;
}

/* Dark-mode readability polish for markdown-heavy content */
html[data-theme="dark"] .single .content blockquote,
html[data-theme="dark"] .problem-content blockquote {
  background: #303228;
  border-left: 4px solid #66d9ef;
  color: #e8e8df;
  margin: 1rem 0;
  padding: 0.6rem 0.9rem;
}

html[data-theme="dark"] .single .content table,
html[data-theme="dark"] .problem-content table {
  border-collapse: collapse;
  width: 100%;
}

html[data-theme="dark"] .single .content th,
html[data-theme="dark"] .single .content td,
html[data-theme="dark"] .problem-content th,
html[data-theme="dark"] .problem-content td {
  border: 1px solid var(--color-border);
  padding: 0.45rem 0.6rem;
}

html[data-theme="dark"] .single .content th,
html[data-theme="dark"] .problem-content th {
  background: #34362c;
  color: #f8f8f2;
}

html[data-theme="dark"] .single .content a,
html[data-theme="dark"] .problem-content a {
  color: #78e6ff;
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.12em;
}

html[data-theme="dark"] .single .content ul li,
html[data-theme="dark"] .single .content ol li,
html[data-theme="dark"] .problem-content ul li,
html[data-theme="dark"] .problem-content ol li {
  margin-bottom: 0.2rem;
}

/* Problem Page */
.problem {
  max-width: 820px;
  margin: 0 auto;
}

.problem-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-border);
}

.problem-meta {
  display: flex;
  gap: 1rem;
  align-items: center;
  flex-wrap: wrap;
  row-gap: 0.35rem;
  margin-bottom: 0.72rem;
}

.problem-id {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--color-text-muted);
  background: var(--color-card-bg);
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
}

.problem-status,
.status {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
}

.status-p-complete {
  background: rgba(5, 150, 105, 0.1);
  color: var(--color-p-complete);
}

.status-p-hard {
  background: rgba(220, 38, 38, 0.1);
  color: var(--color-p-hard);
}

.status-open {
  background: rgba(217, 119, 6, 0.1);
  color: var(--color-open);
}

.problem-header h1 {
  margin: 0.5rem 0;
  font-size: 2rem;
}

.acronym {
  color: var(--color-text-muted);
  font-weight: normal;
}

.problem-category {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.problem-tags-row {
  margin-top: 0.72rem;
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  gap: 0.42rem;
}

.problem-tags-label {
  font-size: 0.84rem;
  color: var(--color-text-muted);
  margin-top: 0.14rem;
}

.problem-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.tag {
  display: inline-block;
  background: var(--color-card-bg);
  color: var(--color-text-muted);
  padding: 0.2rem 0.5rem;
  border-radius: 3px;
  font-size: 0.8rem;
}

.problem-content h2 {
  font-size: 1.3rem;
  margin-top: 2rem;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}

.problem-content h2:first-child {
  margin-top: 0;
}

.problem-content p {
  margin: 0 0 var(--space-4);
}

.problem-content blockquote {
  margin: 0 0 var(--space-4);
  border-radius: var(--radius-sm);
}

.problem-content pre {
  margin: 0 0 var(--space-4);
}

.problem-content table {
  font-size: 0.94rem;
}

.problem-references,
.problem-related {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
}

.problem-references h2,
.problem-related h2 {
  font-size: 1.1rem;
  margin-top: 0;
}

.problem-references ul,
.problem-related ul {
  margin: 0;
  padding-left: 1.25rem;
}

.problem-references li,
.problem-related li {
  margin-bottom: 0.5rem;
}

.problem-content .reference-citation {
  text-decoration: none;
}

.problem-content .reference-citation:hover {
  text-decoration: underline;
}

.problem-references li.reference-item {
  scroll-margin-top: 1.5rem;
  border-radius: 4px;
  padding: 0.15rem 0.3rem;
  transition: background-color 0.4s ease;
}

.problem-references li.reference-item:target,
.problem-references li.reference-item.reference-item-highlight {
  background: rgba(37, 99, 235, 0.12);
  box-shadow: inset 0 0 0 1px rgba(37, 99, 235, 0.22);
}

html[data-theme="dark"] .problem-references li.reference-item:target,
html[data-theme="dark"] .problem-references li.reference-item.reference-item-highlight {
  background: rgba(102, 217, 239, 0.18);
  box-shadow: inset 0 0 0 1px rgba(102, 217, 239, 0.35);
}

@keyframes reference-highlight-flash {
  0% {
    background: rgba(37, 99, 235, 0.26);
    box-shadow: inset 0 0 0 1px rgba(37, 99, 235, 0.32);
  }
  100% {
    background: rgba(37, 99, 235, 0.12);
    box-shadow: inset 0 0 0 1px rgba(37, 99, 235, 0.22);
  }
}

@keyframes reference-highlight-flash-dark {
  0% {
    background: rgba(102, 217, 239, 0.3);
    box-shadow: inset 0 0 0 1px rgba(102, 217, 239, 0.45);
  }
  100% {
    background: rgba(102, 217, 239, 0.18);
    box-shadow: inset 0 0 0 1px rgba(102, 217, 239, 0.35);
  }
}

.problem-references li.reference-item.reference-item-highlight {
  animation: reference-highlight-flash 1.4s ease-out;
}

html[data-theme="dark"] .problem-references li.reference-item.reference-item-highlight {
  animation: reference-highlight-flash-dark 1.4s ease-out;
}

.external-link-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 0.95rem;
  height: 0.95rem;
  margin-left: 0.25rem;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  font-size: 0.75rem;
  line-height: 1;
  color: var(--color-primary);
  text-decoration: none;
  vertical-align: text-top;
}

.external-link-icon .material-symbols-outlined {
  font-size: 0.75rem;
  line-height: 1;
}

.external-link-icon:hover {
  border-color: var(--color-primary);
  background: rgba(37, 99, 235, 0.08);
  text-decoration: none;
}

.relation {
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

/* Problem Page Back Action */
.problem-back-top {
  margin-bottom: 0.85rem;
}

.problem-back-button {
  display: inline-block;
  padding: 0.34rem 0.64rem;
  border-radius: 999px;
  border: 1px solid var(--color-border);
  background: var(--color-card-bg);
  color: var(--color-text-muted);
  font-size: 0.86rem;
  line-height: 1;
  text-decoration: none;
}

.problem-back-button:hover {
  color: var(--color-text);
  border-color: var(--color-primary);
  background: rgba(37, 99, 235, 0.08);
  text-decoration: none;
}

.problem-back-button:focus-visible {
  outline: 2px solid #93c5fd;
  outline-offset: 2px;
}

html[data-theme="dark"] .problem-back-button {
  background: rgba(47, 49, 41, 0.9);
  border-color: var(--color-border);
}

html[data-theme="dark"] .problem-back-button:hover {
  background: rgba(102, 217, 239, 0.14);
  border-color: rgba(102, 217, 239, 0.5);
}

/* Problems List */
.problems-list header {
  margin-bottom: 2rem;
}

.problems-list h1 {
  margin: 0 0 0.5rem 0;
}

.problems-list .description {
  color: var(--color-text-muted);
  margin: 0;
}

.search-filters {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  align-items: start;
  --search-filters-density-gap: var(--space-4);
  --search-filters-density-padding: var(--space-4);
  gap: var(--search-filters-density-gap);
  margin-bottom: var(--space-5);
  padding: var(--search-filters-density-padding);
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
}

.search-box {
  width: 100%;
  min-width: 240px;
  padding: 0.65rem 0.8rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.97rem;
  background: var(--color-bg);
  color: var(--color-text);
}

.search-box-modern:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.16);
}

.filter-group {
  min-width: 0;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.45rem;
}

.search-filters .filter-group:first-child {
  grid-column: 1 / -1;
}

.search-filters .filter-group:first-child .search-box {
  padding: 0.82rem 1rem;
  font-size: 1.05rem;
}

.search-filters .filter-group:not(:first-child) .search-label {
  font-size: 0.76rem;
}

.search-filters .filter-group:not(:first-child) .multi-select-toggle {
  padding: 0.55rem 0.72rem;
  font-size: 0.89rem;
}

.search-label {
  display: inline-block;
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--color-text-muted);
}

.multi-select {
  width: 100%;
  position: relative;
}

.multi-select-toggle {
  width: 100%;
  text-align: left;
  padding: calc(var(--space-3) - 0.1rem) calc(var(--space-4) - 0.2rem);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  color: var(--color-text);
  font-size: 0.95rem;
  cursor: pointer;
}

.multi-select-toggle:focus-visible {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.16);
}

.multi-select-panel {
  position: absolute;
  z-index: 20;
  top: calc(100% + 0.35rem);
  left: 0;
  right: 0;
  max-height: 220px;
  overflow-y: auto;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg);
  box-shadow: var(--shadow-md);
  padding: 0.35rem;
}

.multi-select-option {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  border-radius: 6px;
  padding: 0.35rem 0.4rem;
}

.multi-select-option:hover {
  background: rgba(37, 99, 235, 0.08);
}

.selected-chips {
  margin-top: 0.45rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.filter-chip {
  background: rgba(37, 99, 235, 0.1);
  color: var(--color-primary);
  border: 1px solid rgba(37, 99, 235, 0.28);
  border-radius: 999px;
  padding: 0.2rem 0.55rem;
  font-size: 0.8rem;
  cursor: pointer;
}

.filter-chip:hover {
  background: rgba(37, 99, 235, 0.2);
}

html[data-theme="dark"] .filter-chip {
  background: rgba(102, 217, 239, 0.15);
  border-color: rgba(102, 217, 239, 0.4);
  color: #9defff;
}

.problems-count {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.problems-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  width: 100%;
}

@media (max-width: 920px) {
  .search-filters {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .search-filters {
    grid-template-columns: 1fr;
  }
}

.problem-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--space-4);
  transition: box-shadow 0.2s ease;
}

.problem-card:hover {
  box-shadow: var(--shadow-sm);
}

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.problem-card h2 {
  margin: 0 0 0.5rem 0;
  font-size: 1.1rem;
  line-height: 1.3;
}

.problem-card h2 a {
  color: var(--color-text);
}

.problem-card h2 a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.card-category {
  color: var(--color-text-muted);
  font-size: 0.88rem;
  margin-bottom: 0.35rem;
}

.card-tags-row {
  margin-top: 0.2rem;
  display: flex;
  align-items: flex-start;
  gap: 0.4rem;
}

.card-tags-label {
  font-size: 0.84rem;
  color: var(--color-text-muted);
  margin-top: 0.15rem;
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.problem-tags .tag {
  font-size: 0.8rem;
  padding: 0.16rem 0.5rem;
}

.tag-topic {
  background: rgba(5, 150, 105, 0.14);
  border: 1px solid rgba(5, 150, 105, 0.26);
  color: var(--color-accent);
  border-radius: 999px;
  padding: 0.18rem 0.55rem;
}

html[data-theme="dark"] .tag-topic {
  background: rgba(166, 226, 46, 0.14);
  border-color: rgba(166, 226, 46, 0.34);
  color: #c7f56b;
}

/* Home Page */
.home-hero {
  text-align: center;
  padding: 1.4rem 0 2.4rem;
  max-width: var(--content-width);
  margin: 0 auto;
}

.home-hero h1 {
  font-size: 2.15rem;
  margin: 0 0 0.45rem;
}

.home-hero .lead {
  font-size: 1.02rem;
  color: var(--color-text-muted);
  margin-bottom: 1rem;
}

.home-cta {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.home-cta-advanced {
  justify-content: center;
  margin-top: 1rem;
}

.home-cta-advanced .problem-back-button {
  opacity: 0.86;
}

.home-cta-advanced .problem-back-button:hover,
.home-cta-advanced .problem-back-button:focus-visible {
  opacity: 1;
}

.home-search-panel {
  margin: 0 auto;
  max-width: 760px;
  text-align: left;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: var(--color-card-bg);
  padding: var(--space-5);
}

.home-search-box {
  position: relative;
  margin-top: 0.35rem;
}

.home-search-box .search-box {
  min-height: calc(var(--space-4) * 3);
  padding: calc(var(--space-5) - 0.4rem) calc(var(--space-5) - 0.3rem);
  font-size: 1.04rem;
}

.home-search-results {
  list-style: none;
  margin: 0.35rem 0 0;
  padding: 0.35rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg);
  max-height: 320px;
  overflow-y: auto;
}

.home-search-option {
  margin: 0;
}

.home-search-hit {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: var(--color-text);
  text-align: left;
  padding: 0.45rem 0.5rem;
  cursor: pointer;
}

.home-search-hit:hover,
.home-search-option.is-active .home-search-hit {
  background: rgba(37, 99, 235, 0.11);
}

.home-search-name {
  font-size: 0.95rem;
}

html[data-theme="dark"] .home-search-hit:hover,
html[data-theme="dark"] .home-search-option.is-active .home-search-hit {
  background: rgba(102, 217, 239, 0.16);
}

.home-content {
  margin-top: 0.2rem;
}

.home-page-footer-cta {
  margin-top: 2.2rem;
  display: flex;
  justify-content: center;
}

.is-home .container {
  padding-top: 1rem;
}

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border-radius: 6px;
  font-weight: 500;
  text-decoration: none;
}

.btn-compact {
  padding: 0.42rem 0.88rem;
  font-size: 0.86rem;
}

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

.btn-primary:hover {
  background: var(--color-primary-dark);
  text-decoration: none;
}

.btn-secondary {
  background: var(--color-card-bg);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  background: var(--color-border);
  text-decoration: none;
}

.btn-secondary {
  background: var(--color-card-bg);
}

/* KaTeX overrides for inline math */
.katex {
  font-size: 1.05em;
}

/* Problems Hub */
.problems-hub header {
  margin-bottom: 1.5rem;
}

.problems-hub h1 {
  margin: 0 0 0.5rem 0;
}

.problems-hub .description {
  color: var(--color-text-muted);
  margin: 0;
}

.hub-actions {
  margin-bottom: 2rem;
}

.problems-hub h2 {
  margin-bottom: 1rem;
  font-size: 1.3rem;
}

/* Categories Grid */
.categories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.category-card {
  display: block;
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 1.25rem;
  text-decoration: none;
  transition: box-shadow 0.2s ease, border-color 0.2s ease;
}

.category-card:hover {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  border-color: var(--color-primary);
  text-decoration: none;
}

.category-card h2 {
  margin: 0 0 0.5rem 0;
  font-size: 1.1rem;
  color: var(--color-text);
}

.category-card .count {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.back-link {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--color-border);
}

/* Responsive */
@media (max-width: 768px) {
  .container {
    padding: 1.35rem 1rem;
  }

  .nav-container {
    flex-direction: column;
    text-align: center;
  }

  .nav-controls {
    flex-direction: column;
  }
  
  .nav-menu {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  .problems-grid {
    grid-template-columns: 1fr;
  }

  .search-filters {
    gap: var(--space-3);
  }

  .problem-card {
    padding: var(--space-3);
  }
  
  .home-hero h1 {
    font-size: 1.75rem;
  }

  .home-search-panel {
    padding: var(--space-4);
  }
  
}