/* CSS Variables */
:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --background: #f8fafc;
    --surface: #ffffff;
    --surface-hover: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --transition: all 0.2s ease;
}

/* Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* Base Styles */
html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* App Container */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #1d4ed8 100%);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-img {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-md);
}

.header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    letter-spacing: -0.025em;
}

.tagline {
    font-size: 1rem;
    opacity: 0.9;
}

/* Tabs */
.tabs {
    display: flex;
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
    padding: 0 1rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.tab-btn {
    flex: 1;
    min-width: fit-content;
    padding: 1rem 1.5rem;
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

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

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

/* Main Content */
.main-content {
    flex: 1;
    padding: 1.5rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

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

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

/* Converter Section */
.converter-container {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.current-time-display {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    text-align: center;
    box-shadow: var(--shadow-md);
}

.current-time-display h2 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.5rem;
}

.time-display {
    font-size: 3rem;
    font-weight: 700;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
}

.date-display {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.timezone-info {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
}

/* Converter Form */
.converter-form {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.timezone-select,
.datetime-input,
.date-input {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    color: var(--text-primary);
    background: var(--surface);
    transition: var(--transition);
    width: 100%;
}

.timezone-select:focus,
.datetime-input:focus,
.date-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.swap-btn {
    align-self: center;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: 2px solid var(--border-color);
    background: var(--surface);
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.swap-btn:hover {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: rotate(180deg);
}

.result-container {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    text-align: center;
    border: 1px solid #bae6fd;
}

.result-container h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--primary-color);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.5rem;
}

.converted-time {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
}

.converted-date {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.dst-indicator {
    font-size: 0.875rem;
    margin-top: 0.5rem;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    display: inline-block;
}

.dst-indicator.dst-active {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning-color);
}

.dst-indicator.dst-inactive {
    background: rgba(100, 116, 139, 0.1);
    color: var(--secondary-color);
}

/* Multi-timezone Section */
.multi-timezone-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
}

.multi-timezone-section h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.add-timezone-row {
    display: flex;
    gap: 0.5rem;
}

.add-timezone-row .timezone-select {
    flex: 1;
}

.add-btn {
    padding: 0.75rem 1.25rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

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

.multi-timezone-results {
    margin-top: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.timezone-result-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.timezone-result-item .tz-name {
    font-weight: 500;
    color: var(--text-primary);
}

.timezone-result-item .tz-time {
    font-size: 1.25rem;
    font-weight: 600;
    font-variant-numeric: tabular-nums;
}

.timezone-result-item .tz-date {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.remove-btn {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    border: none;
    background: var(--danger-color);
    color: white;
    cursor: pointer;
    font-size: 1.25rem;
    line-height: 1;
    transition: var(--transition);
}

.remove-btn:hover {
    background: #dc2626;
    transform: scale(1.1);
}

/* World Clock */
.world-clock-container h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.world-clock-controls {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.world-clock-controls .timezone-select {
    flex: 1;
    max-width: 400px;
}

.world-clock-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1rem;
}

.clock-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    position: relative;
    overflow: hidden;
}

.clock-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--primary-color);
}

.clock-card.daytime::before {
    background: linear-gradient(90deg, #f59e0b, #fbbf24);
}

.clock-card.nighttime::before {
    background: linear-gradient(90deg, #3b82f6, #6366f1);
}

.clock-card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.clock-card-city {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.clock-card-offset {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.clock-card-time {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
}

.clock-card-date {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.clock-card-dst {
    font-size: 0.75rem;
    color: var(--warning-color);
    margin-top: 0.5rem;
}

.clock-card .remove-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    opacity: 0;
    transition: var(--transition);
}

.clock-card:hover .remove-btn {
    opacity: 1;
}

/* Meeting Planner */
.meeting-planner-container h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.section-description {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.meeting-setup {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.working-hours {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.working-hours input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
}

.working-hours span {
    color: var(--text-secondary);
}

.participants-section h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.add-participant-row {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.add-participant-row input[type="text"] {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    flex: 1;
    min-width: 150px;
}

.add-participant-row .timezone-select {
    flex: 2;
    min-width: 200px;
}

.participants-list {
    margin-top: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.participant-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.participant-info {
    display: flex;
    flex-direction: column;
}

.participant-name {
    font-weight: 500;
    color: var(--text-primary);
}

.participant-tz {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.primary-btn {
    padding: 1rem 2rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.primary-btn:disabled {
    background: var(--text-muted);
    cursor: not-allowed;
    transform: none;
}

/* Meeting Results */
.meeting-results {
    margin-top: 1.5rem;
}

.meeting-results h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.time-slots {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.time-slot {
    background: var(--surface);
    border-radius: var(--radius-md);
    padding: 1rem 1.25rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.time-slot.good {
    border-left: 4px solid var(--success-color);
}

.time-slot.okay {
    border-left: 4px solid var(--warning-color);
}

.time-slot.bad {
    border-left: 4px solid var(--danger-color);
}

.time-slot-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.time-slot-time {
    font-size: 1.125rem;
    font-weight: 600;
}

.time-slot-score {
    font-size: 0.875rem;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
}

.time-slot.good .time-slot-score {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success-color);
}

.time-slot.okay .time-slot-score {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning-color);
}

.time-slot.bad .time-slot-score {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger-color);
}

.time-slot-details {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
}

.participant-time {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.participant-time strong {
    color: var(--text-primary);
}

/* Footer */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border-color);
    padding: 1.5rem;
    text-align: center;
    margin-top: auto;
}

.footer p {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .header {
        padding: 1.5rem 1rem;
    }

    .header h1 {
        font-size: 1.5rem;
    }

    .tabs {
        padding: 0;
    }

    .tab-btn {
        padding: 0.875rem 1rem;
        font-size: 0.875rem;
    }

    .main-content {
        padding: 1rem;
    }

    .time-display {
        font-size: 2.25rem;
    }

    .converted-time {
        font-size: 2rem;
    }

    .clock-card-time {
        font-size: 2rem;
    }

    .world-clock-controls {
        flex-direction: column;
    }

    .world-clock-controls .timezone-select {
        max-width: 100%;
    }

    .add-participant-row {
        flex-direction: column;
    }

    .add-participant-row input[type="text"],
    .add-participant-row .timezone-select {
        width: 100%;
    }

    .working-hours {
        flex-wrap: wrap;
    }

    .working-hours input {
        flex: 1;
        min-width: 100px;
    }

    .time-slot-details {
        flex-direction: column;
        gap: 0.5rem;
    }
}

@media (max-width: 480px) {
    .logo {
        flex-direction: column;
    }

    .time-display {
        font-size: 2rem;
    }

    .converted-time {
        font-size: 1.75rem;
    }

    .clock-card-time {
        font-size: 1.75rem;
    }

    .timezone-result-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .timezone-result-item .remove-btn {
        align-self: flex-end;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --background: #0f172a;
        --surface: #1e293b;
        --surface-hover: #334155;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --text-muted: #64748b;
        --border-color: #334155;
    }

    .result-container {
        background: linear-gradient(135deg, #1e3a5f 0%, #1e293b 100%);
        border-color: #3b82f6;
    }

    .timezone-select,
    .datetime-input,
    .date-input,
    .working-hours input,
    .add-participant-row input[type="text"] {
        background: var(--surface);
        color: var(--text-primary);
    }
}