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

:root {
    --primary: #2196F3;
    --success: #4CAF50;
    --warning: #FFC107;
    --danger: #F44336;
    --purple: #9C27B0;
    --white: #ffffff;
    --light-gray: #f5f5f5;
    --gray: #757575;
    --dark-gray: #424242;
    --black: #212121;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
    --border-radius: 12px;
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    color: var(--black);
    line-height: 1.6;
    min-height: 100vh;
    padding-bottom: 80px;
}

/* Header */
.app-header {
    background: var(--white);
    padding: 1rem;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    border-bottom: 3px solid var(--primary);
}

.app-header h1 {
    font-size: 1.5rem;
    color: var(--primary);
    margin-bottom: 0.5rem;
    text-align: center;
    font-weight: 700;
}

.header-stats {
    display: flex;
    justify-content: space-around;
    gap: 1rem;
}

.stat-item {
    text-align: center;
    flex: 1;
}

.stat-value {
    display: block;
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--primary);
}

.stat-label {
    font-size: 0.8rem;
    color: var(--gray);
}

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

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

.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;
    flex-wrap: wrap;
    gap: 1rem;
}

.section-header h2 {
    color: var(--dark-gray);
    font-size: 1.5rem;
    font-weight: 600;
}

/* Cards */
.card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
    border: 1px solid #e0e0e0;
    transition: var(--transition);
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0,0,0,0.15);
}

.card h3 {
    color: var(--dark-gray);
    margin-bottom: 1rem;
    font-size: 1.2rem;
    font-weight: 600;
}

/* Dashboard Grid */
.dashboard-grid {
    display: grid;
    gap: 1rem;
    margin-bottom: 2rem;
}

@media (min-width: 768px) {
    .dashboard-grid {
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    }
}

/* Quick Actions */
.quick-actions {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.action-btn {
    background: var(--white);
    border: 2px solid var(--primary);
    border-radius: var(--border-radius);
    padding: 1rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    color: var(--primary);
    font-weight: 500;
}

.action-btn:hover {
    background: var(--primary);
    color: var(--white);
    transform: translateY(-2px);
}

.action-btn i {
    font-size: 1.5rem;
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: 500;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: var(--transition);
    font-size: 0.9rem;
}

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

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

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

.btn-secondary:hover {
    background: #616161;
}

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

.btn-success:hover {
    background: #388E3C;
}

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

.btn-danger:hover {
    background: #D32F2F;
}

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

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

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid #e0e0e0;
    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);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 1.5rem;
    flex-wrap: wrap;
}

/* Lists */
.empty-state {
    text-align: center;
    color: var(--gray);
    font-style: italic;
    padding: 2rem;
}

.usage-list,
.distractions-list,
.goals-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.usage-item,
.distraction-item,
.goal-item {
    background: var(--light-gray);
    border-radius: 8px;
    padding: 1rem;
    border-left: 4px solid var(--primary);
}

.usage-item h4,
.distraction-item h4,
.goal-item h4 {
    margin-bottom: 0.5rem;
    color: var(--dark-gray);
}

.usage-item p,
.distraction-item p,
.goal-item p {
    color: var(--gray);
    font-size: 0.9rem;
    margin: 0.25rem 0;
}

/* Goals Grid */
.goals-grid {
    display: grid;
    gap: 1rem;
}

@media (min-width: 768px) {
    .goals-grid {
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    }
}

.goal-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    border-left: 4px solid var(--success);
}

.goal-card.overdue {
    border-left-color: var(--danger);
}

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

.progress-bar {
    background: #e0e0e0;
    border-radius: 10px;
    height: 8px;
    overflow: hidden;
}

.progress-fill {
    background: var(--success);
    height: 100%;
    border-radius: 10px;
    transition: width 0.3s ease;
}

/* Challenges */
.challenges-grid {
    display: grid;
    gap: 1rem;
}

@media (min-width: 768px) {
    .challenges-grid {
        grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    }
}

.challenge-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    border: 1px solid #e0e0e0;
    transition: var(--transition);
}

.challenge-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0,0,0,0.15);
}

.challenge-difficulty {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

.difficulty-easy {
    background: rgba(76, 175, 80, 0.1);
    color: var(--success);
}

.difficulty-medium {
    background: rgba(255, 193, 7, 0.1);
    color: var(--warning);
}

.difficulty-hard {
    background: rgba(244, 67, 54, 0.1);
    color: var(--danger);
}

/* Statistics */
.stats-overview {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 1rem;
}

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

.stat-number {
    display: block;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary);
}

.stat-desc {
    color: var(--gray);
    font-size: 0.9rem;
}

.charts-container {
    display: grid;
    gap: 1rem;
    margin-bottom: 2rem;
}

@media (min-width: 768px) {
    .charts-container {
        grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    }
}

.chart-card {
    background: var(--white);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
}

.chart-card canvas {
    max-width: 100%;
    height: auto;
}

/* Time Filter */
.time-filter {
    display: flex;
    gap: 0.5rem;
    background: var(--light-gray);
    border-radius: var(--border-radius);
    padding: 0.25rem;
}

.filter-btn {
    padding: 0.5rem 1rem;
    border: none;
    background: transparent;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.9rem;
}

.filter-btn.active,
.filter-btn:hover {
    background: var(--primary);
    color: var(--white);
}

/* FAQ */
.faq-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.faq-item {
    background: var(--white);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.faq-question {
    width: 100%;
    padding: 1.5rem;
    border: none;
    background: transparent;
    text-align: left;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: var(--dark-gray);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-question:hover {
    background: var(--light-gray);
}

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

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

.faq-answer {
    border-top: 1px solid #e0e0e0;
    padding: 1.5rem;
    background: var(--light-gray);
    animation: slideDown 0.3s ease;
}

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

@keyframes slideDown {
    from {
        opacity: 0;
        max-height: 0;
        padding: 0 1.5rem;
    }
    to {
        opacity: 1;
        max-height: 200px;
        padding: 1.5rem;
    }
}

/* Bottom Navigation */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--white);
    display: flex;
    justify-content: space-around;
    padding: 0.5rem 0;
    box-shadow: 0 -2px 8px rgba(0,0,0,0.1);
    border-top: 1px solid #e0e0e0;
    z-index: 1000;
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-decoration: none;
    color: var(--gray);
    padding: 0.5rem;
    border-radius: 8px;
    transition: var(--transition);
    min-width: 60px;
    font-size: 0.75rem;
}

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

/* Footer */
footer {
    text-align: center;
    padding: 2rem 1rem 1rem;
    color: var(--gray);
    font-size: 0.9rem;
    margin-top: 2rem;
}

/* Responsive Design */
@media (max-width: 480px) {
    .app-header h1 {
        font-size: 1.3rem;
    }
    
    .section-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .quick-actions {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .nav-item span {
        display: none;
    }
    
    .bottom-nav {
        padding: 0.75rem 0;
    }
}

@media (min-width: 768px) {
    .app-main {
        padding: 2rem;
    }
    
    .dashboard-grid {
        grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    }
    
    .quick-actions {
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
        max-width: 600px;
    }
}

@media (min-width: 1024px) {
    .app-header {
        padding: 1.5rem 2rem;
    }
    
    .bottom-nav {
        max-width: 800px;
        left: 50%;
        transform: translateX(-50%);
        border-radius: var(--border-radius) var(--border-radius) 0 0;
    }
}

/* Animations */
.fade-in {
    animation: fadeIn 0.5s ease;
}

.slide-up {
    animation: slideUp 0.3s ease;
}

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

/* Loading States */
.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 2rem;
    color: var(--gray);
}

.loading::after {
    content: '';
    width: 20px;
    height: 20px;
    border: 2px solid #e0e0e0;
    border-top: 2px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-left: 0.5rem;
}

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

/* Success/Error Messages */
.message {
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    font-weight: 500;
}

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

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

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --white: #1e1e1e;
        --light-gray: #2d2d2d;
        --gray: #888;
        --dark-gray: #e0e0e0;
        --black: #ffffff;
    }
    
    body {
        background: linear-gradient(135deg, #1e1e1e 0%, #2d2d2d 100%);
    }
}