:root {
    --bg-primary: #1a1d24;
    --bg-secondary: #24272f;
    --bg-tertiary: #2d3139;
    --text-primary: #e8eaed;
    --text-secondary: #9aa0a6;
    --accent: #78828d;
    --accent-hover: #959da5;
    --border: #3c3f47;
    --success: #4caf50;
    --danger: #f44336;
    --shadow: rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    text-align: center;
    padding: 20px 0;
    margin-bottom: 20px;
}

header h1 {
    font-size: 2rem;
    font-weight: 600;
}

/* Tab Navigation */
.tab-nav {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--border);
}

.tab-btn {
    flex: 1;
    padding: 12px 16px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    border-bottom: 3px solid transparent;
    font-weight: 500;
}

.tab-btn:hover {
    color: var(--text-primary);
}

.tab-btn.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

/* Tab Content */
.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* Form Styles */
.input-section,
.list-section,
.analytics-section,
.settings-section {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 24px;
    box-shadow: 0 2px 8px var(--shadow);
}

.settings-section {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
}

.input-section h2,
.list-section h2,
.analytics-section h2,
.settings-section h2 {
    margin-bottom: 20px;
    font-size: 1.5rem;
}

.settings-section h2 {
    flex-basis: 100%;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: var(--text-primary);
    font-weight: 500;
    font-size: 0.95rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--accent);
}

.duration-control {
    display: flex;
    gap: 8px;
    align-items: center;
}

.duration-control input {
    flex: 1;
}

.btn-adjust {
    padding: 12px 20px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    min-width: 60px;
}

.btn-adjust:hover {
    background: var(--border);
}

.btn-primary {
    width: 100%;
    padding: 14px 24px;
    background: var(--accent);
    border: none;
    border-radius: 8px;
    color: white;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s ease;
}

.btn-primary:hover {
    background: var(--accent-hover);
}

.btn-secondary {
    padding: 12px 24px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    display: inline-block;
}

.btn-secondary:hover {
    background: var(--border);
}

/* Filter Controls */
.list-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 16px;
    margin-bottom: 20px;
}

.search-filter-controls {
    display: flex;
    flex-direction: column;
    gap: 12px;
    flex: 1;
}

.search-box {
    position: relative;
    max-width: 400px;
}

.search-input {
    width: 100%;
    padding: 10px 36px 10px 12px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.search-input:focus {
    outline: none;
    border-color: var(--accent);
}

.search-clear {
    position: absolute;
    right: 8px;
    top: 50%;
    transform: translateY(-50%);
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.search-clear:hover {
    background: var(--border);
    color: var(--text-primary);
}

.filter-controls {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.filter-btn:hover {
    color: var(--text-primary);
}

.filter-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* Statistics Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(192px, 1fr));
    gap: 12px;
    margin-bottom: 20px;
}

.stat-card {
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px;
    text-align: center;
}

.stat-value {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--accent);
    margin-bottom: 4px;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Pagination */
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 16px;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border);
}

.btn-page {
    padding: 8px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.9rem;
}

.btn-page:hover:not(:disabled) {
    background: var(--border);
}

.btn-page:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

#page-info {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Activity List */
#activity-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.activity-item {
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.activity-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow);
}

.activity-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 12px;
}

.activity-name {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--accent);
    text-transform: capitalize;
}

.activity-actions {
    display: flex;
    gap: 8px;
}

.btn-edit,
.btn-delete {
    padding: 6px 12px;
    border: none;
    border-radius: 6px;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

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

.btn-edit:hover {
    background: var(--accent-hover);
}

.btn-edit:disabled {
    background: var(--border);
    cursor: not-allowed;
    opacity: 0.5;
}

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

.btn-delete:hover {
    background: #d32f2f;
}

.activity-meta {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 8px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.activity-details {
    margin-top: 8px;
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-style: italic;
}

.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
}

/* Analytics */
.analytics-section {
    padding: 16px !important;
}

.analytics-section h2 {
    font-size: 1.3rem !important;
    margin-bottom: 12px !important;
}

.analytics-controls {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
    padding: 12px;
    background: var(--bg-tertiary);
    border-radius: 6px;
    border: 1px solid var(--border);
}

.control-group {
    display: flex;
    align-items: center;
    gap: 8px;
    margin: 0;
}

.control-group label {
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin: 0;
}

.control-group select {
    padding: 6px 12px;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text-primary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.control-group select:hover {
    border-color: var(--accent);
}

.control-group select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(168, 178, 189, 0.1);
}

.navigation-controls {
    display: flex;
    align-items: center;
    gap: 12px;
}

.btn-nav {
    padding: 6px 14px;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.85rem;
    font-weight: 500;
}

.btn-nav:hover {
    background: var(--border);
    color: var(--text-primary);
    border-color: var(--accent);
}

#current-period-label {
    font-weight: 600;
    color: var(--accent);
    font-size: 0.95rem;
    min-width: 140px;
    text-align: center;
    letter-spacing: 0.3px;
}

.chart-container {
    position: relative;
    height: 380px;
    background: var(--bg-tertiary);
    border-radius: 6px;
    padding: 12px;
    border: 1px solid var(--border);
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.2);
}

/* Settings */
.settings-card {
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 20px;
    flex-basis: calc(50% - 01.5rem);
}

.settings-card:last-child {
    flex-basis: 100%;
}

.settings-card h3 {
    margin-bottom: 16px;
    font-size: 1.2rem;
}

.warning-text {
    color: var(--danger);
    font-size: 0.9rem;
    margin-bottom: 12px;
    padding: 8px;
    background: rgba(244, 67, 54, 0.1);
    border-radius: 4px;
}

.btn-danger {
    width: 100%;
    padding: 14px 24px;
    background: var(--danger);
    border: none;
    border-radius: 8px;
    color: white;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s ease;
}

.btn-danger:hover {
    background: #d32f2f;
}

.data-actions {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 24px;
    max-width: 500px;
    width: 90%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 8px 32px var(--shadow);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.modal-header h2 {
    font-size: 1.5rem;
}

.modal-close {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 2rem;
    cursor: pointer;
    line-height: 1;
    padding: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 4px;
    transition: all 0.3s ease;
}

.modal-close:hover {
    background: var(--border);
    color: var(--text-primary);
}

/* Validation Error */
.validation-error {
    background-color: var(--danger);
    color: white;
    padding: 12px 16px;
    border-radius: 8px;
    margin-bottom: 16px;
    font-size: 0.95rem;
    animation: slideDown 0.3s ease;
}

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

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 12px;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .tab-btn {
        padding: 10px 12px;
        font-size: 0.9rem;
    }

    .input-section,
    .list-section,
    .analytics-section,
    .settings-section {
        padding: 16px;
    }

    .settings-card {
        flex-basis: 100%;
    }

    .list-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .filter-controls {
        width: 100%;
        justify-content: space-between;
    }

    .filter-btn {
        flex: 1;
    }

    .analytics-controls {
        flex-direction: column;
        align-items: stretch;
        gap: 10px;
    }

    .control-group {
        flex-direction: column;
        align-items: stretch;
    }

    .control-group select {
        width: 100%;
    }

    .chart-container {
        height: 280px;
    }

    .navigation-controls {
        flex-wrap: wrap;
        justify-content: center;
    }

    #current-period-label {
        flex-basis: 100%;
        order: -1;
        margin-bottom: 6px;
    }
}