:root {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface2: #273449;
    --border: #334155;
    --text: #e2e8f0;
    --text-muted: #94a3b8;
    --accent: #3b82f6;
    --bronze: #ad5600;
    --silver: #435f7a;
    --gold: #d97706;
    --platinum: #059669;
    --diamond: #0284c7;
    --ruby: #e11d48;
    --unrated: #64748b;
}
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    font-family: "Inter", sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
}

/* Header */
header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--border);
    padding: 0 24px;
    height: 60px;
    display: flex;
    align-items: center;
    gap: 16px;
}
.site-logo {
    display: flex;
    align-items: center;
    flex-shrink: 0;
    text-decoration: none;
}
.site-logo img {
    width: 28px;
    height: 28px;
}
.github-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: 7px;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-muted);
    background: var(--surface2);
    border: 1px solid var(--border);
    text-decoration: none;
    transition: all 0.15s;
    white-space: nowrap;
    flex-shrink: 0;
}
.github-btn:hover {
    color: var(--text);
    border-color: var(--text-muted);
}
#search {
    flex: 1;
    max-width: 480px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 8px 14px;
    color: var(--text);
    font-size: 14px;
    font-family: "Inter", sans-serif;
    outline: none;
    transition: border-color 0.2s;
}
#search:focus {
    border-color: var(--accent);
}
#search::placeholder {
    color: var(--text-muted);
}
.header-stat {
    color: var(--text-muted);
    font-size: 13px;
    white-space: nowrap;
    margin-left: auto;
}

/* Filters */
.filters {
    padding: 12px 24px;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    align-items: center;
}
.filter-label {
    font-size: 12px;
    color: var(--text-muted);
    margin-right: 4px;
}
.tier-btn {
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    border: 2px solid transparent;
    transition: all 0.15s;
    background: var(--surface2);
}
.tier-btn.active,
.tier-btn:hover {
    opacity: 1;
}
.tier-btn:not(.active) {
    opacity: 0.6;
}
.divider {
    width: 1px;
    height: 20px;
    background: var(--border);
    margin: 0 4px;
}
#tag-select {
    background: var(--surface2);
    border: 1px solid var(--border);
    color: var(--text);
    border-radius: 6px;
    padding: 4px 8px;
    font-size: 12px;
    cursor: pointer;
    outline: none;
}
.clear-btn {
    padding: 4px 10px;
    border-radius: 6px;
    font-size: 12px;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-muted);
    cursor: pointer;
}
.clear-btn:hover {
    border-color: var(--text-muted);
    color: var(--text);
}

/* Main */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px 24px;
}

/* Problem Table */
.problem-table {
    width: 100%;
    border-collapse: collapse;
}
.problem-table th {
    text-align: left;
    padding: 10px 14px;
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}
.problem-table th:last-child {
    text-align: right;
}
.problem-row {
    border-bottom: 1px solid var(--border);
    cursor: pointer;
    transition: background 0.1s;
}
.problem-row:hover {
    background: var(--surface);
}
.problem-row td {
    padding: 12px 14px;
    font-size: 14px;
}
.problem-num {
    color: var(--text-muted);
    font-size: 13px;
    font-family: "JetBrains Mono", monospace;
}
.problem-title {
    font-weight: 500;
}
.tier-badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 12px;
    font-size: 11px;
    font-weight: 700;
    white-space: nowrap;
}
.tag-list {
    display: flex;
    gap: 4px;
    flex-wrap: wrap;
}
.tag {
    padding: 2px 8px;
    border-radius: 12px;
    font-size: 11px;
    background: var(--surface2);
    color: var(--text-muted);
    white-space: nowrap;
}
.accept-count {
    text-align: right;
    color: var(--text-muted);
    font-size: 13px;
    font-family: "JetBrains Mono", monospace;
}

/* Pagination */
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    padding: 24px 0;
}
.page-btn {
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 14px;
    cursor: pointer;
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text);
    transition: all 0.1s;
}
.page-btn:hover:not(:disabled) {
    border-color: var(--accent);
    color: var(--accent);
}
.page-btn.active {
    background: var(--accent);
    border-color: var(--accent);
    color: white;
}
.page-btn:disabled {
    opacity: 0.3;
    cursor: default;
}
.page-info {
    color: var(--text-muted);
    font-size: 14px;
}

/* Modal */
.modal-overlay {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 200;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    overflow-y: auto;
    padding: 40px 20px;
}
.modal-overlay.open {
    display: flex;
    justify-content: center;
    align-items: flex-start;
}
.modal {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    width: 100%;
    max-width: 860px;
    padding: 32px;
    position: relative;
}
.modal-close {
    position: absolute;
    top: 16px;
    right: 16px;
    background: var(--surface2);
    border: 1px solid var(--border);
    color: var(--text-muted);
    border-radius: 6px;
    width: 32px;
    height: 32px;
    font-size: 18px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}
.modal-close:hover {
    color: var(--text);
}
.modal-header {
    margin-bottom: 20px;
}
.modal-num {
    font-size: 13px;
    color: var(--text-muted);
    margin-bottom: 4px;
}
.modal-title {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 10px;
}
.modal-meta {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    align-items: center;
}
.meta-item {
    font-size: 13px;
    color: var(--text-muted);
}
.meta-item span {
    color: var(--text);
}
.modal-tags {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
    margin-top: 10px;
}
.modal-tag {
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 12px;
    background: var(--surface2);
    color: var(--text-muted);
    cursor: pointer;
    border: 1px solid var(--border);
}
.modal-tag:hover {
    border-color: var(--accent);
    color: var(--accent);
}
.modal-divider {
    border: none;
    border-top: 1px solid var(--border);
    margin: 20px 0;
}
.modal-section-title {
    font-size: 13px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 10px;
}
.modal-section {
    margin-bottom: 24px;
}

/* Problem HTML content */
.problem-content {
    line-height: 1.8;
    font-size: 15px;
}
.problem-content p {
    margin-bottom: 12px;
}
.problem-content pre {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 12px 16px;
    font-family: "JetBrains Mono", monospace;
    font-size: 13px;
    overflow-x: auto;
    margin-bottom: 12px;
}
.problem-content code {
    font-family: "JetBrains Mono", monospace;
    font-size: 13px;
    background: var(--bg);
    padding: 1px 5px;
    border-radius: 4px;
}
.problem-content img {
    max-width: 100%;
    height: auto;
    border-radius: 6px;
}
.problem-content img[src] {
    display: block;
    margin: 12px 0;
}
.problem-content table {
    border-collapse: collapse;
    margin-bottom: 12px;
}
.problem-content td,
.problem-content th {
    border: 1px solid var(--border);
    padding: 6px 12px;
    font-size: 14px;
}
.problem-content ul,
.problem-content ol {
    padding-left: 20px;
    margin-bottom: 12px;
}

/* Sample I/O */
.sample-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}
.sample-box {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    overflow: hidden;
}
.sample-box-header {
    padding: 6px 12px;
    font-size: 11px;
    font-weight: 600;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}
.sample-box pre {
    padding: 12px;
    font-family: "JetBrains Mono", monospace;
    font-size: 13px;
    white-space: pre-wrap;
    word-break: break-all;
}

/* Python Runner */
.py-runner {
    margin-top: 8px;
}
.py-textarea {
    width: 100%;
    resize: vertical;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 12px;
    color: var(--text);
    font-family: "JetBrains Mono", monospace;
    font-size: 13px;
    line-height: 1.6;
    outline: none;
    transition: border-color 0.2s;
    tab-size: 4;
    box-sizing: border-box;
}
.py-textarea:focus {
    border-color: var(--accent);
}
.py-top-actions {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-top: 10px;
}
.py-run-all-btn {
    padding: 7px 18px;
    border-radius: 7px;
    font-size: 13px;
    font-weight: 600;
    background: var(--accent);
    border: none;
    color: #fff;
    cursor: pointer;
    transition: opacity 0.15s;
}
.py-run-all-btn:hover:not(:disabled) {
    opacity: 0.85;
}
.py-run-all-btn:disabled {
    opacity: 0.45;
    cursor: default;
}
.py-status {
    font-size: 13px;
    font-weight: 600;
    color: var(--text-muted);
}
.py-chips-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 6px;
    margin-top: 12px;
}
.py-chip {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 5px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 500;
    border: 1px solid var(--border);
    background: var(--surface2);
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.15s;
    white-space: nowrap;
}
.py-chip:hover {
    border-color: var(--text-muted);
    color: var(--text);
}
.py-chip.active {
    border-color: var(--accent);
    color: var(--accent);
}
.py-chip.pass {
    color: #10b981;
    background: #10b98112;
    border-color: #10b98144;
}
.py-chip.pass.active {
    border-color: #10b981;
}
.py-chip.fail {
    color: #ef4444;
    background: #ef444412;
    border-color: #ef444444;
}
.py-chip.fail.active {
    border-color: #ef4444;
}
.py-chip.error {
    color: #f59e0b;
    background: #f59e0b12;
    border-color: #f59e0b44;
}
.py-chip.error.active {
    border-color: #f59e0b;
}
.py-chip.running {
    opacity: 0.5;
    cursor: default;
    pointer-events: none;
}
.py-chip-icon {
    font-size: 12px;
}
.py-chip-add {
    color: var(--accent);
    border-color: var(--accent);
    background: transparent;
}
.py-chip-add:hover {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}
.py-details {
    margin-top: 8px;
}
.py-detail {
    display: none;
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
    margin-bottom: 6px;
}
.py-detail.open {
    display: block;
}
.py-detail-header {
    display: flex;
    align-items: center;
    padding: 8px 12px;
    background: var(--surface2);
    border-bottom: 1px solid var(--border);
    font-size: 12px;
    font-weight: 600;
    color: var(--text-muted);
}
.py-detail-del {
    margin-left: auto;
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 11px;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.15s;
}
.py-detail-del:hover {
    border-color: #ef4444;
    color: #ef4444;
}
.py-detail-grid {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
}
.py-detail-col {
    padding: 10px 12px;
    min-width: 0;
}
.py-detail-col + .py-detail-col {
    border-left: 1px solid var(--border);
}
.py-detail-col-label {
    font-size: 11px;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin-bottom: 6px;
}
.py-detail-pre {
    font-family: "JetBrains Mono", monospace;
    font-size: 12px;
    line-height: 1.5;
    color: var(--text);
    white-space: pre-wrap;
    word-break: break-all;
    margin: 0;
    min-height: 36px;
}
.py-detail-pre.muted {
    color: var(--text-muted);
}
.py-detail-pre.py-stderr {
    color: #f87171;
}
.py-detail-pre .py-stderr {
    display: block;
    color: #f87171;
}
.py-detail-ta {
    width: 100%;
    resize: vertical;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 7px 9px;
    color: var(--text);
    font-family: "JetBrains Mono", monospace;
    font-size: 12px;
    line-height: 1.5;
    outline: none;
    box-sizing: border-box;
    min-height: 36px;
}
.py-detail-ta:focus {
    border-color: var(--accent);
}
.runner-lang-row {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}
.runner-lang-select {
    background: var(--surface2);
    border: 1px solid var(--border);
    color: var(--text);
    border-radius: 6px;
    padding: 5px 10px;
    font-size: 13px;
    font-family: "JetBrains Mono", monospace;
    cursor: pointer;
    outline: none;
}
.runner-lang-select:focus {
    border-color: var(--accent);
}
.runner-lang-hint {
    font-size: 11px;
    color: var(--text-muted);
}

/* Loading / Error */
.loading {
    text-align: center;
    padding: 60px;
    color: var(--text-muted);
}
.spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--border);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.7s linear infinite;
    margin: 0 auto 12px;
}
@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}
.empty {
    text-align: center;
    padding: 60px;
    color: var(--text-muted);
    font-size: 15px;
}

/* Footer */
.site-footer {
    text-align: center;
    padding: 24px 16px;
    font-size: 12px;
    color: #64748b;
    border-top: 1px solid #1e293b;
    margin-top: 32px;
    line-height: 1.8;
}
.site-footer a {
    color: #64748b;
}

/* Tier button colors */
.tier-btn[data-tier="all"] {
    color: #e2e8f0;
}
.tier-btn[data-tier="0"] {
    color: var(--unrated);
}
.tier-btn[data-tier="1-5"] {
    color: var(--bronze);
}
.tier-btn[data-tier="6-10"] {
    color: var(--silver);
}
.tier-btn[data-tier="11-15"] {
    color: var(--gold);
}
.tier-btn[data-tier="16-20"] {
    color: var(--platinum);
}
.tier-btn[data-tier="21-25"] {
    color: var(--diamond);
}
.tier-btn[data-tier="26-30"] {
    color: var(--ruby);
}

@media (max-width: 640px) {
    .tag-list,
    .accept-count {
        display: none;
    }
    .sample-grid {
        grid-template-columns: 1fr;
    }
    .modal {
        padding: 20px;
    }
    .py-detail-grid {
        grid-template-columns: 1fr;
    }
    .py-detail-col + .py-detail-col {
        border-left: none;
        border-top: 1px solid var(--border);
    }
}