:root {
    --primary-color: #2196F3;
    --success-color: #4CAF50;
    --warning-color: #FFC107;
    --danger-color: #F44336;
    --purple-color: #9C27B0;
    --background-color: #f5f5f5;
    --surface-color: #ffffff;
    --text-primary: #212121;
    --text-secondary: #757575;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
    --shadow-hover: 0 4px 12px rgba(0,0,0,0.15);
    --border-radius: 8px;
    --transition: all 0.3s ease;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    padding-bottom: 80px;
}

/* Header */
.app-header {
    background: var(--primary-color);
    color: white;
    padding: 1rem;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
}

.app-title {
    font-size: 1.2rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.header-actions {
    display: flex;
    gap: 0.5rem;
}

.language-toggle {
    background: rgba(255,255,255,0.2);
    border: none;
    color: white;
    padding: 0.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.25rem;
    font-size: 0.9rem;
    transition: var(--transition);
}

.language-toggle:hover {
    background: rgba(255,255,255,0.3);
}

/* Main Content */
.app-main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem;
}

.app-section {
    display: none;
    animation: fadeIn 0.3s ease;
}

.app-section.active {
    display: block;
}

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

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.section-header h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

/* Forms */
.meeting-form {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

.form-group textarea {
    min-height: 80px;
    resize: vertical;
}

/* Buttons */
.btn-primary,
.btn-secondary,
.btn-danger {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    justify-content: center;
}

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

.btn-primary:hover {
    background: #1976D2;
    transform: translateY(-1px);
    box-shadow: var(--shadow-hover);
}

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

.btn-secondary:hover {
    background: var(--background-color);
    transform: translateY(-1px);
}

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

.btn-danger:hover {
    background: #d32f2f;
    transform: translateY(-1px);
}

/* Participants */
.participants-section {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.participants-section h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.participants-list {
    margin-bottom: 1rem;
}

.participant-item {
    background: var(--background-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 0.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.participant-info h4 {
    margin-bottom: 0.25rem;
    color: var(--text-primary);
}

.participant-info p {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.participant-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-icon {
    background: none;
    border: none;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-secondary);
}

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

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

/* Meetings List */
.meetings-list {
    display: grid;
    gap: 1rem;
}

.meeting-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    transition: var(--transition);
}

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

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

.meeting-card h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.meeting-card-date {
    font-weight: 600;
    color: var(--primary-color);
}

.meeting-card-description {
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.meeting-participants {
    margin-bottom: 1rem;
}

.meeting-participants h4 {
    font-size: 0.9rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.participants-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.participant-chip {
    background: var(--background-color);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    color: var(--text-primary);
}

.meeting-actions {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

/* Filter Controls */
.filter-controls select {
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--surface-color);
}

/* Timezone Converter */
.timezone-converter {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.converter-row {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 1rem;
    align-items: end;
    margin-bottom: 2rem;
}

.timezone-input {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.timezone-input label {
    font-weight: 500;
    color: var(--text-primary);
}

.timezone-input select,
.timezone-input input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

.converter-arrow {
    color: var(--primary-color);
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.world-clocks h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.clocks-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.clock-item {
    background: var(--background-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    text-align: center;
}

.clock-item h4 {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.clock-time {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
}

.clock-date {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Settings */
.settings-content {
    display: grid;
    gap: 2rem;
}

.setting-group {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.setting-group h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.setting-item {
    margin-bottom: 1rem;
}

.setting-item label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.setting-item input,
.setting-item select {
    width: 100%;
    max-width: 300px;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
}

/* FAQ */
.faq-section {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-top: 2rem;
}

.faq-section h2 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.faq-container {
    display: grid;
    gap: 0.5rem;
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    overflow: hidden;
}

.faq-question {
    width: 100%;
    padding: 1rem;
    background: var(--background-color);
    border: none;
    text-align: left;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-primary);
    transition: var(--transition);
}

.faq-question:hover {
    background: #eeeeee;
}

.faq-question[aria-expanded="true"] {
    background: var(--primary-color);
    color: white;
}

.faq-question[aria-expanded="true"] .faq-icon {
    transform: rotate(45deg);
}

.faq-icon {
    font-size: 1.2rem;
    transition: var(--transition);
}

.faq-answer {
    padding: 1rem;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    animation: slideDown 0.3s ease;
}

.faq-answer[hidden] {
    display: none;
}

@keyframes slideDown {
    from {
        opacity: 0;
        max-height: 0;
        padding-top: 0;
        padding-bottom: 0;
    }
    to {
        opacity: 1;
        max-height: 200px;
        padding-top: 1rem;
        padding-bottom: 1rem;
    }
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    color: var(--border-color);
}

.empty-state h3 {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

/* Bottom Navigation */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-around;
    padding: 0.5rem 0;
    z-index: 1000;
    box-shadow: 0 -2px 8px rgba(0,0,0,0.1);
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 0.5rem;
    text-decoration: none;
    color: var(--text-secondary);
    transition: var(--transition);
    min-width: 60px;
}

.nav-item i {
    font-size: 1.2rem;
    margin-bottom: 0.25rem;
}

.nav-item span {
    font-size: 0.7rem;
    font-weight: 500;
}

.nav-item.active {
    color: var(--primary-color);
}

.nav-item:hover {
    color: var(--primary-color);
}

/* Modals */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.5);
    z-index: 2000;
    padding: 1rem;
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-hover);
    width: 100%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
    animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(-50px) scale(0.9);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h3 {
    color: var(--text-primary);
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0.25rem;
}

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

.modal form {
    padding: 1.5rem;
}

.modal-actions {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: 1rem;
    justify-content: flex-end;
}

/* Time Slots */
.time-slots-content {
    padding: 1.5rem;
    max-height: 400px;
    overflow-y: auto;
}

.time-slot {
    background: var(--background-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    border-left: 4px solid var(--success-color);
}

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

.time-slot.fair {
    border-left-color: var(--warning-color);
}

.time-slot.poor {
    border-left-color: var(--danger-color);
}

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

.time-slot-time {
    font-weight: 600;
    color: var(--text-primary);
}

.time-slot-quality {
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
    color: white;
}

.time-slot-quality.excellent {
    background: var(--success-color);
}

.time-slot-quality.good {
    background: var(--success-color);
}

.time-slot-quality.fair {
    background: var(--warning-color);
}

.time-slot-quality.poor {
    background: var(--danger-color);
}

.time-slot-participants {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    background: var(--surface-color);
    margin-top: 2rem;
    border-top: 1px solid var(--border-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .app-title {
        font-size: 1rem;
    }
    
    .app-title span {
        display: none;
    }
    
    .converter-row {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .converter-arrow {
        transform: rotate(90deg);
    }
    
    .clocks-grid {
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    }
    
    .meeting-card-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }
    
    .meeting-actions {
        justify-content: stretch;
    }
    
    .meeting-actions .btn-secondary {
        flex: 1;
        min-width: 0;
    }
    
    .modal-actions {
        flex-direction: column-reverse;
    }
    
    .modal-actions .btn-primary,
    .modal-actions .btn-secondary {
        width: 100%;
    }
}

@media (min-width: 769px) {
    .app-main {
        padding: 2rem;
    }
    
    .meetings-list {
        grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    }
    
    .bottom-nav {
        display: none;
    }
    
    body {
        padding-bottom: 0;
    }
    
    .app-section {
        display: block;
    }
    
    .app-section:not(.active) {
        display: none;
    }
    
    .app-header {
        position: static;
    }
    
    .section-header {
        position: sticky;
        top: 0;
        background: var(--background-color);
        padding: 1rem 0;
        z-index: 10;
    }
}

/* Loading States */
.loading {
    opacity: 0.6;
    pointer-events: none;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    margin: -10px 0 0 -10px;
    border: 2px solid var(--primary-color);
    border-top-color: transparent;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* Success/Error Messages */
.message {
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.message.success {
    background: rgba(76, 175, 80, 0.1);
    color: var(--success-color);
    border: 1px solid rgba(76, 175, 80, 0.3);
}

.message.error {
    background: rgba(244, 67, 54, 0.1);
    color: var(--danger-color);
    border: 1px solid rgba(244, 67, 54, 0.3);
}

.message.warning {
    background: rgba(255, 193, 7, 0.1);
    color: #f57c00;
    border: 1px solid rgba(255, 193, 7, 0.3);
}