:root {
    --primary-color: #007AFF;
    --secondary-color: #5AC8FA;
    --success-color: #34C759;
    --warning-color: #FF9500;
    --danger-color: #FF3B30;
    --dark-color: #1C1C1E;
    --gray-1: #8E8E93;
    --gray-2: #C7C7CC;
    --gray-3: #D1D1D6;
    --gray-4: #E5E5EA;
    --gray-5: #F2F2F7;
    --white: #FFFFFF;
    --shadow-light: 0 2px 15px rgba(0, 0, 0, 0.08);
    --shadow-medium: 0 4px 20px rgba(0, 0, 0, 0.12);
    --shadow-heavy: 0 8px 30px rgba(0, 0, 0, 0.18);
    --border-radius: 12px;
    --border-radius-large: 20px;
    --transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--dark-color);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

.app-container {
    min-height: 100vh;
    background: var(--gray-5);
}

/* Navigation Bar */
.nav-bar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-light);
}

.nav-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.logo-icon {
    font-size: 1.5rem;
}

.nav-links {
    display: flex;
    gap: 0.5rem;
}

.nav-link {
    background: transparent;
    border: none;
    padding: 0.5rem 1.2rem;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--gray-1);
    cursor: pointer;
    transition: var(--transition);
}

.nav-link:hover {
    background: var(--gray-5);
    color: var(--dark-color);
}

.nav-link.active {
    background: var(--primary-color);
    color: var(--white);
}

.language-toggle {
    background: transparent;
    border: 1px solid var(--gray-3);
    padding: 0.5rem 1rem;
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--dark-color);
    cursor: pointer;
    transition: var(--transition);
}

.language-toggle:hover {
    background: var(--gray-5);
}

/* Main Content */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

.section {
    display: none;
    animation: fadeIn 0.5s ease;
}

.section.active {
    display: block;
}

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

/* Glass Card Effect */
.glass-card {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-radius: var(--border-radius-large);
    padding: 1.5rem;
    box-shadow: var(--shadow-light);
    border: 1px solid rgba(255, 255, 255, 0.5);
    transition: var(--transition);
}

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

/* Dashboard Section */
.hero-card {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding: 2rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: var(--white);
}

.greeting {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

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

.weather-widget {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.weather-icon {
    font-size: 3rem;
}

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

.temp {
    font-size: 1.5rem;
    font-weight: 600;
}

.conditions {
    font-size: 0.9rem;
    opacity: 0.9;
}

/* Quick Stats */
.quick-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    padding: 1.5rem;
}

.stat-icon {
    font-size: 2.5rem;
}

.stat-info h3 {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--gray-1);
    margin-bottom: 0.25rem;
}

.stat-value {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--dark-color);
}

.stat-change {
    font-size: 0.85rem;
    color: var(--success-color);
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--gray-4);
    border-radius: 3px;
    overflow: hidden;
    margin-top: 0.5rem;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    border-radius: 3px;
    transition: width 0.5s ease;
}

/* Today's Plan */
.today-plan h2 {
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
}

.workout-card {
    background: linear-gradient(135deg, #f5f5f5, #ffffff);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 1rem;
}

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

.workout-details {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    color: var(--gray-1);
}

.route-suggestion {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    color: var(--dark-color);
}

/* Buttons */
.btn-primary {
    background: var(--primary-color);
    color: var(--white);
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary:hover {
    background: #0051D5;
    transform: scale(1.02);
}

.btn-secondary {
    background: var(--gray-5);
    color: var(--dark-color);
    border: 1px solid var(--gray-3);
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-secondary:hover {
    background: var(--gray-4);
}

.btn-small {
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
    border-radius: 8px;
    background: var(--primary-color);
    color: var(--white);
    border: none;
    cursor: pointer;
    font-weight: 500;
    transition: var(--transition);
}

.btn-small:hover {
    background: #0051D5;
}

/* Training Section */
.section-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 2rem;
}

.training-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2rem;
}

.tab-btn {
    background: transparent;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 500;
    color: var(--gray-1);
    cursor: pointer;
    transition: var(--transition);
}

.tab-btn:hover {
    background: var(--gray-5);
}

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

.plans-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.plan-card {
    padding: 1.5rem;
    transition: var(--transition);
}

.plan-card.active-plan {
    border: 2px solid var(--primary-color);
}

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

.plan-header h3 {
    font-size: 1.2rem;
    font-weight: 600;
}

.duration {
    background: var(--gray-5);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.85rem;
    color: var(--gray-1);
}

.plan-description {
    color: var(--gray-1);
    margin-bottom: 1rem;
    font-size: 0.95rem;
}

.plan-stats {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    font-size: 0.85rem;
    color: var(--gray-1);
}

/* Week Schedule */
.week-schedule h2 {
    margin-bottom: 1.5rem;
}

.schedule-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 1rem;
}

.day-schedule {
    text-align: center;
}

.day-header {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-bottom: 0.5rem;
}

.day {
    font-size: 0.85rem;
    color: var(--gray-1);
    font-weight: 500;
}

.date {
    font-size: 1.2rem;
    font-weight: 600;
}

.workout-pill {
    background: var(--gray-5);
    padding: 0.5rem;
    border-radius: 8px;
    font-size: 0.8rem;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.workout-pill.complete {
    background: var(--success-color);
    color: var(--white);
}

.workout-pill.today {
    background: var(--primary-color);
    color: var(--white);
}

.workout-pill.rest {
    background: var(--gray-4);
    color: var(--gray-1);
}

/* Workout Generator */
.workout-generator {
    max-width: 800px;
}

.generator-controls {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

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

.control-group label {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--gray-1);
}

.select-input, .input-field {
    padding: 0.75rem;
    border: 1px solid var(--gray-3);
    border-radius: var(--border-radius);
    font-size: 1rem;
    background: var(--white);
    transition: var(--transition);
}

.select-input:focus, .input-field:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.1);
}

/* Pace Calculator */
.pace-calculator {
    max-width: 800px;
}

.calculator-grid {
    display: grid;
    grid-template-columns: 1fr 2fr auto;
    gap: 1.5rem;
    align-items: end;
    margin-bottom: 2rem;
}

.time-inputs {
    display: flex;
    gap: 0.5rem;
}

.time-inputs input {
    width: 60px;
}

.pace-result {
    background: var(--gray-5);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 2rem;
    text-align: center;
    min-height: 100px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.predictions-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
}

/* Analytics Charts */
.analytics-overview {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.chart-card {
    padding: 2rem;
}

.chart-card h3 {
    margin-bottom: 1.5rem;
    font-size: 1.2rem;
}

#weeklyChart, #paceChart {
    width: 100%;
    height: 250px;
}

/* Personal Records */
.pr-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
}

.pr-item {
    background: linear-gradient(135deg, #f5f5f5, #ffffff);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    text-align: center;
}

.pr-distance {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.pr-time {
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 0.25rem;
}

.pr-date {
    font-size: 0.85rem;
    color: var(--gray-1);
    margin-bottom: 0.25rem;
}

.pr-pace {
    font-size: 0.9rem;
    color: var(--dark-color);
}

/* Stats Summary */
.summary-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
}

.summary-stat {
    text-align: center;
}

.stat-label {
    display: block;
    font-size: 0.9rem;
    color: var(--gray-1);
    margin-bottom: 0.5rem;
}

.stat-big {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: var(--dark-color);
    margin-bottom: 0.25rem;
}

.stat-sub {
    display: block;
    font-size: 0.85rem;
    color: var(--gray-1);
}

/* Community Section */
.community-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

/* Leaderboard */
.leaderboard-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.leaderboard-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--gray-5);
    border-radius: var(--border-radius);
}

.leaderboard-item.you {
    background: linear-gradient(135deg, #007AFF20, #5AC8FA20);
    border: 1px solid var(--primary-color);
}

.rank {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--white);
    border-radius: 50%;
    font-weight: 700;
}

.rank.gold {
    background: linear-gradient(135deg, #FFD700, #FFA500);
    color: var(--white);
}

.rank.silver {
    background: linear-gradient(135deg, #C0C0C0, #808080);
    color: var(--white);
}

.rank.bronze {
    background: linear-gradient(135deg, #CD7F32, #B87333);
    color: var(--white);
}

.runner-info {
    flex: 1;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.runner-name {
    font-weight: 600;
}

.runner-stats {
    color: var(--gray-1);
}

/* Challenges */
.challenge-list {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.challenge-item {
    display: flex;
    gap: 1rem;
    padding: 1rem;
    background: var(--gray-5);
    border-radius: var(--border-radius);
}

.challenge-icon {
    font-size: 2rem;
}

.challenge-info {
    flex: 1;
}

.challenge-info h4 {
    margin-bottom: 0.25rem;
}

.challenge-info p {
    font-size: 0.9rem;
    color: var(--gray-1);
    margin-bottom: 0.5rem;
}

.challenge-progress {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.challenge-progress span {
    font-size: 0.85rem;
    color: var(--gray-1);
}

/* Group Runs */
.run-list {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.run-item {
    display: flex;
    gap: 1rem;
    padding: 1rem;
    background: var(--gray-5);
    border-radius: var(--border-radius);
}

.run-date {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--white);
    padding: 0.75rem;
    border-radius: var(--border-radius);
    min-width: 60px;
}

.run-date .day {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.run-date .month {
    font-size: 0.85rem;
    color: var(--gray-1);
}

.run-details {
    flex: 1;
}

.run-details h4 {
    margin-bottom: 0.5rem;
}

.run-details p {
    font-size: 0.9rem;
    color: var(--gray-1);
    margin-bottom: 0.25rem;
}

.participants {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 0.5rem;
}

.participant-count {
    font-size: 0.85rem;
    color: var(--success-color);
}

/* Achievements */
.badge-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 1rem;
}

.badge {
    background: var(--gray-5);
    padding: 1rem;
    border-radius: var(--border-radius);
    text-align: center;
    opacity: 0.5;
    filter: grayscale(1);
    transition: var(--transition);
}

.badge.earned {
    opacity: 1;
    filter: grayscale(0);
    background: linear-gradient(135deg, #f5f5f5, #ffffff);
}

.badge-icon {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.badge-name {
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.badge-desc {
    font-size: 0.75rem;
    color: var(--gray-1);
}

/* Floating Action Button */
.fab {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: var(--white);
    border: none;
    box-shadow: var(--shadow-heavy);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    cursor: pointer;
    transition: var(--transition);
    z-index: 999;
}

.fab:hover {
    transform: scale(1.1);
    box-shadow: 0 10px 40px rgba(0, 122, 255, 0.3);
}

.fab:active {
    transform: scale(0.95);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-content {
        padding: 1rem;
    }

    .nav-links {
        display: none;
    }

    .main-content {
        padding: 1rem;
    }

    .hero-card {
        flex-direction: column;
        text-align: center;
        gap: 2rem;
    }

    .quick-stats {
        grid-template-columns: 1fr;
    }

    .schedule-grid {
        grid-template-columns: repeat(4, 1fr);
        font-size: 0.8rem;
    }

    .calculator-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }

    .analytics-overview {
        grid-template-columns: 1fr;
    }

    .community-grid {
        grid-template-columns: 1fr;
    }
}

/* Animations */
@keyframes slideIn {
    from {
        transform: translateX(-100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

@keyframes pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(0, 122, 255, 0.4);
    }
    70% {
        box-shadow: 0 0 0 10px rgba(0, 122, 255, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(0, 122, 255, 0);
    }
}

.fab-icon {
    animation: pulse 2s infinite;
}