:root {
    --primary-color: #2196F3;
    --success-color: #4CAF50;
    --warning-color: #FFC107;
    --danger-color: #F44336;
    --purple-color: #9C27B0;
    --background-color: #f5f5f5;
    --surface-color: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --shadow: 0 2px 10px rgba(0,0,0,0.1);
    --shadow-hover: 0 4px 20px rgba(0,0,0,0.15);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    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;
    overflow-x: hidden;
    padding-bottom: 80px;
}

.app-header {
    background: linear-gradient(135deg, var(--primary-color), var(--purple-color));
    color: white;
    padding: 1rem;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

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

.header-content h1 {
    font-size: 1.5rem;
    font-weight: 700;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-icon {
    background: rgba(255,255,255,0.2);
    border: none;
    color: white;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
}

.btn-icon:hover {
    background: rgba(255,255,255,0.3);
    transform: scale(1.05);
}

.main-content {
    margin-top: 80px;
    padding: 1rem;
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
}

.page-section {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.section-header h2 {
    font-size: 1.8rem;
    color: var(--text-primary);
}

.dashboard-grid {
    display: grid;
    gap: 1.5rem;
    grid-template-columns: 1fr;
}

@media (min-width: 768px) {
    .dashboard-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (min-width: 1024px) {
    .dashboard-grid {
        grid-template-columns: 2fr 1fr;
        grid-template-rows: auto auto;
    }
    
    .progress-chart-container {
        grid-row: 1 / 3;
    }
}

.stats-card {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: linear-gradient(135deg, #f8f9ff, #e8f2ff);
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.stat-icon {
    font-size: 2rem;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--primary-color);
    border-radius: 50%;
    color: white;
}

.stat-info h3 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

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

.progress-chart-container {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
}

.progress-chart-container h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

#progressChart {
    width: 100%;
    height: auto;
    border-radius: 8px;
}

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

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

.activities-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.activity-item {
    padding: 1rem;
    background: #f8f9fa;
    border-radius: 8px;
    border-left: 4px solid var(--success-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.activity-info {
    flex: 1;
}

.activity-info strong {
    color: var(--text-primary);
}

.activity-time {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

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

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.skills-grid {
    display: grid;
    gap: 1.5rem;
    grid-template-columns: 1fr;
}

@media (min-width: 768px) {
    .skills-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1024px) {
    .skills-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

.skill-card {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

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

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

.skill-title {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.skill-level {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
}

.skill-progress {
    margin: 1rem 0;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: #e0e0e0;
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--success-color));
    border-radius: 4px;
    transition: width 0.5s ease;
}

.progress-text {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
    text-align: right;
}

.skill-actions {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
}

.btn-small {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 500;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

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

.btn-secondary {
    background: var(--text-secondary);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-secondary:hover {
    background: #555;
    transform: translateY(-1px);
}

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

.btn-success:hover {
    background: #45a049;
}

.btn-warning {
    background: var(--warning-color);
    color: #333;
}

.btn-warning:hover {
    background: #e6ac00;
}

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

.btn-danger:hover {
    background: #da190b;
}

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

.gap-item {
    padding: 1rem;
    border-left: 4px solid var(--warning-color);
    background: #fff8e1;
    border-radius: 8px;
    margin-bottom: 1rem;
}

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

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

.gap-priority {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
    margin-top: 0.5rem;
}

.gap-priority.high {
    background: var(--danger-color);
    color: white;
}

.gap-priority.medium {
    background: var(--warning-color);
    color: #333;
}

.gap-priority.low {
    background: var(--success-color);
    color: white;
}

.schedule-container {
    display: grid;
    gap: 2rem;
    grid-template-columns: 1fr;
}

@media (min-width: 768px) {
    .schedule-container {
        grid-template-columns: 1fr 1fr;
    }
}

.time-tracker {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow);
    text-align: center;
}

.timer-display {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-color);
    margin: 2rem 0;
    font-family: 'Courier New', monospace;
}

.timer-controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.current-session {
    margin-top: 1rem;
    padding: 1rem;
    background: #e8f5e8;
    border-radius: 8px;
    border-left: 4px solid var(--success-color);
}

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

.session-item {
    padding: 1rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    margin-bottom: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

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

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

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

.achievements-grid {
    display: grid;
    gap: 1.5rem;
    grid-template-columns: 1fr;
}

@media (min-width: 768px) {
    .achievements-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1024px) {
    .achievements-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

.achievement-card {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow);
    text-align: center;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.achievement-card.unlocked {
    background: linear-gradient(135deg, #fff3e0, #e8f5e8);
    border: 2px solid var(--success-color);
}

.achievement-card.locked {
    opacity: 0.6;
    filter: grayscale(50%);
}

.achievement-card:hover {
    transform: translateY(-2px);
}

.achievement-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

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

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

.faq-section {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: var(--shadow);
}

.faq-section h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--text-primary);
}

.faq-container {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 1rem;
}

.faq-question {
    width: 100%;
    padding: 1.5rem 0;
    background: none;
    border: none;
    text-align: left;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    transition: var(--transition);
}

.faq-question:hover {
    color: var(--primary-color);
}

.faq-icon {
    font-size: 1.2rem;
    font-weight: 300;
    transition: transform 0.3s ease;
}

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

.faq-answer {
    padding: 0 0 1.5rem 0;
    color: var(--text-secondary);
    line-height: 1.6;
    animation: slideDown 0.3s ease;
}

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

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

.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 10px 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);
    border-radius: 8px;
    min-width: 60px;
}

.nav-item:hover,
.nav-item.active {
    color: var(--primary-color);
    background: rgba(33, 150, 243, 0.1);
}

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

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

.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.5);
    backdrop-filter: blur(5px);
}

.modal.active {
    display: flex;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.3s ease;
}

.modal-content {
    background: var(--surface-color);
    margin: 1rem;
    padding: 2rem;
    border-radius: var(--border-radius);
    width: 100%;
    max-width: 500px;
    position: relative;
    box-shadow: var(--shadow-hover);
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.close {
    position: absolute;
    right: 1rem;
    top: 1rem;
    font-size: 1.5rem;
    font-weight: bold;
    cursor: pointer;
    color: var(--text-secondary);
    transition: var(--transition);
}

.close:hover {
    color: var(--danger-color);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: var(--transition);
    background: var(--surface-color);
}

.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 {
    resize: vertical;
    min-height: 100px;
}

footer {
    background: var(--text-primary);
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    margin-top: 3rem;
}

footer p {
    margin: 0;
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .main-content {
        padding: 0.5rem;
    }
    
    .section-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .section-header h2 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
    }
    
    .timer-display {
        font-size: 2rem;
    }
    
    .timer-controls {
        gap: 0.5rem;
    }
    
    .btn-primary,
    .btn-secondary {
        padding: 0.6rem 1rem;
        font-size: 0.9rem;
    }
    
    .modal-content {
        margin: 0.5rem;
        padding: 1.5rem;
    }
    
    .nav-item span {
        font-size: 0.65rem;
    }
}

.notification {
    position: fixed;
    top: 100px;
    right: 1rem;
    background: var(--success-color);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-hover);
    z-index: 3000;
    animation: slideInRight 0.3s ease, fadeOut 0.3s ease 2.7s;
    max-width: 300px;
}

.notification.error {
    background: var(--danger-color);
}

.notification.warning {
    background: var(--warning-color);
    color: #333;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(100%);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes fadeOut {
    from {
        opacity: 1;
    }
    to {
        opacity: 0;
    }
}

.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid #f3f3f3;
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}