* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary: #2563eb;
    --secondary: #6366f1;
    --accent: #f59e0b;
    --yellow: #f5c518;
    --yellow-light: #fff9e6;
    --yellow-dark: #b8860b;
    --green: #6aaa64;
    --green-light: #e8f5e9;
    --green-dark: #2e7d32;
    --blue: #5dadec;
    --blue-light: #e3f2fd;
    --blue-dark: #1565c0;
    --purple: #ba81c5;
    --purple-light: #f3e5f5;
    --purple-dark: #6a1b9a;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-tertiary: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 20px rgba(0,0,0,0.15);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 0;
    min-height: 100vh;
}

.navbar {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.navbar-content {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
    transition: opacity 0.2s;
}

.logo:hover {
    opacity: 0.8;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    background: var(--bg-primary);
    padding: 40px;
}

.top-nav {
    display: flex;
    justify-content: flex-end;
    margin-bottom: 20px;
}

.nav-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    text-decoration: none;
    border-radius: 25px;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.nav-link:hover {
    background: var(--text-primary);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

header {
    text-align: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
}

h1 {
    font-size: clamp(1.5rem, 4vw, 2.5rem);
    margin-bottom: 10px;
    color: var(--text-primary);
    font-weight: 800;
    letter-spacing: -0.5px;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-top: 10px;
}

.date {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 5px;
    font-weight: 500;
}

.editor {
    font-size: 0.9rem;
    color: var(--text-tertiary);
}

.warning-box {
    background: linear-gradient(135deg, #fff8dc 0%, #ffeaa7 100%);
    border-left: 4px solid #f0ad4e;
    padding: 20px;
    margin-bottom: 30px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.warning-box p:first-child {
    font-weight: 700;
    margin-bottom: 8px;
    font-size: 1.05rem;
}

.category {
    margin-bottom: 40px;
    padding: 25px;
    border-radius: var(--border-radius);
    background: var(--bg-tertiary);
    transition: var(--transition);
}

.category:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.category-header {
    margin-bottom: 20px;
}

.difficulty {
    font-size: 0.85rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 5px;
    display: inline-block;
    padding: 6px 14px;
    border-radius: 20px;
}

.category.yellow .difficulty { 
    background: var(--yellow-light);
    color: var(--yellow-dark);
}
.category.green .difficulty { 
    background: var(--green-light);
    color: var(--green-dark);
}
.category.blue .difficulty { 
    background: var(--blue-light);
    color: var(--blue-dark);
}
.category.purple .difficulty { 
    background: var(--purple-light);
    color: var(--purple-dark);
}

.hint-section, .group-section, .words-section {
    margin-bottom: 15px;
}

.reveal-btn {
    background: white;
    border: 2px solid var(--border-color);
    padding: 14px 28px;
    border-radius: 30px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 700;
    transition: var(--transition);
    width: 100%;
    max-width: 220px;
    box-shadow: var(--shadow-sm);
}

.reveal-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none !important;
    box-shadow: var(--shadow-sm) !important;
}

.reveal-btn:disabled:hover {
    transform: none !important;
    box-shadow: var(--shadow-sm) !important;
}

.category.yellow .reveal-btn {
    background: var(--yellow-light);
    color: var(--yellow-dark);
    border-color: var(--yellow);
}

.category.yellow .reveal-btn:hover {
    background: var(--yellow);
    color: white;
}

.category.green .reveal-btn {
    background: var(--green-light);
    color: var(--green-dark);
    border-color: var(--green);
}

.category.green .reveal-btn:hover {
    background: var(--green);
    color: white;
}

.category.blue .reveal-btn {
    background: var(--blue-light);
    color: var(--blue-dark);
    border-color: var(--blue);
}

.category.blue .reveal-btn:hover {
    background: var(--blue);
    color: white;
}

.category.purple .reveal-btn {
    background: var(--purple-light);
    color: var(--purple-dark);
    border-color: var(--purple);
}

.category.purple .reveal-btn:hover {
    background: var(--purple);
    color: white;
}

.revealed-content {
    margin-top: 15px;
    padding: 20px;
    background: white;
    border-radius: var(--border-radius);
    animation: fadeIn 0.3s ease-in-out;
    box-shadow: var(--shadow-sm);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hint-text {
    font-style: italic;
    color: var(--text-secondary);
    line-height: 1.6;
}

.group-name {
    font-weight: 800;
    font-size: 1.2rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.category.yellow .group-name { color: var(--yellow-dark); }
.category.green .group-name { color: var(--green-dark); }
.category.blue .group-name { color: var(--blue-dark); }
.category.purple .group-name { color: var(--purple-dark); }

.words-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 12px;
    margin-top: 10px;
}

.word-btn {
    background: white;
    border: 2px solid var(--border-color);
    padding: 12px 18px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 700;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.word-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.category.yellow .word-btn {
    background: var(--yellow-light);
    color: var(--yellow-dark);
    border-color: var(--yellow);
}

.category.yellow .word-btn:hover {
    background: var(--yellow);
    color: white;
}

.category.green .word-btn {
    background: var(--green-light);
    color: var(--green-dark);
    border-color: var(--green);
}

.category.green .word-btn:hover {
    background: var(--green);
    color: white;
}

.category.blue .word-btn {
    background: var(--blue-light);
    color: var(--blue-dark);
    border-color: var(--blue);
}

.category.blue .word-btn:hover {
    background: var(--blue);
    color: white;
}

.category.purple .word-btn {
    background: var(--purple-light);
    color: var(--purple-dark);
    border-color: var(--purple);
}

.category.purple .word-btn:hover {
    background: var(--purple);
    color: white;
}

.word-revealed {
    padding: 12px 18px;
    border-radius: 20px;
    font-weight: 700;
    text-align: center;
    animation: fadeIn 0.3s ease-in-out;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.category.yellow .word-revealed {
    background: var(--yellow);
    color: white;
}

.category.green .word-revealed {
    background: var(--green);
    color: white;
}

.category.blue .word-revealed {
    background: var(--blue);
    color: white;
}

.category.purple .word-revealed {
    background: var(--purple);
    color: white;
}

footer {
    margin-top: 50px;
    padding-top: 30px;
    border-top: 2px solid var(--border-color);
}

footer h2 {
    font-size: 1.8rem;
    margin-bottom: 15px;
    color: var(--text-primary);
    font-weight: 700;
}

footer h3 {
    font-size: 1.3rem;
    margin-top: 25px;
    margin-bottom: 15px;
    color: var(--text-primary);
    font-weight: 600;
}

footer p {
    color: var(--text-secondary);
    margin-bottom: 15px;
    line-height: 1.7;
}

.color-legend {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.legend-item {
    display: flex;
    align-items: flex-start;
    gap: 15px;
    padding: 15px;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.legend-item:hover {
    background: var(--bg-secondary);
    transform: translateY(-2px);
}

.color-box {
    width: 40px;
    height: 40px;
    border-radius: 10px;
    flex-shrink: 0;
    box-shadow: var(--shadow-sm);
}

.color-box.yellow { background: var(--yellow); }
.color-box.green { background: var(--green); }
.color-box.blue { background: var(--blue); }
.color-box.purple { background: var(--purple); }

.legend-item strong {
    display: block;
    margin-bottom: 3px;
    font-weight: 700;
}

.legend-item p {
    font-size: 0.9rem;
    margin: 0;
}

.hidden {
    display: none;
}

.archive-container {
    padding: 20px 0;
}

.date-filter {
    display: flex;
    gap: 20px;
    margin-bottom: 30px;
    flex-wrap: wrap;
    align-items: center;
    padding: 20px;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius);
}

.date-filter label {
    font-weight: 600;
    color: var(--text-primary);
}

.date-filter select {
    padding: 10px 15px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: white;
    cursor: pointer;
    transition: var(--transition);
}

.date-filter select:hover {
    border-color: var(--blue);
}

.date-filter select:focus {
    outline: none;
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(93, 173, 236, 0.1);
}

.puzzle-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.puzzle-card {
    display: block;
    padding: 20px;
    background: white;
    border-radius: var(--border-radius);
    text-decoration: none;
    color: var(--text-primary);
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
    border: 2px solid transparent;
}

.puzzle-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--blue);
}

.puzzle-card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

.puzzle-card h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.puzzle-id {
    font-size: 0.85rem;
    color: var(--text-tertiary);
    font-weight: 600;
}

.puzzle-categories {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.category-tag {
    font-size: 0.75rem;
    padding: 6px 12px;
    border-radius: 15px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.category-tag.yellow {
    background: var(--yellow-light);
    color: var(--yellow-dark);
}

.category-tag.green {
    background: var(--green-light);
    color: var(--green-dark);
}

.category-tag.blue {
    background: var(--blue-light);
    color: var(--blue-dark);
}

.category-tag.purple {
    background: var(--purple-light);
    color: var(--purple-dark);
}

@media (max-width: 768px) {
    body {
        padding: 10px;
    }

    .container {
        padding: 25px 20px;
    }

    h1 {
        font-size: 1.5rem;
    }

    .words-grid {
        grid-template-columns: 1fr;
    }

    .color-legend {
        grid-template-columns: 1fr;
    }

    .puzzle-list {
        grid-template-columns: 1fr;
    }

    .date-filter {
        flex-direction: column;
        align-items: stretch;
        gap: 15px;
    }

    .date-filter select {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 20px 15px;
    }

    .category {
        padding: 20px 15px;
    }

    .reveal-btn {
        max-width: 100%;
    }
}