:root {
    /* Color Palette */
    --primary: #ff6b35;
    --primary-dark: #e5552a;
    --primary-light: #ff8556;
    --secondary: #4ecdc4;
    --accent: #ffe66d;

    /* Background Colors */
    --bg-primary: #0f0f1e;
    --bg-secondary: #1a1a2e;
    --bg-tertiary: #16213e;
    --bg-card: rgba(26, 26, 46, 0.7);
    --bg-glass: rgba(255, 255, 255, 0.05);

    /* Text Colors */
    --text-primary: #ffffff;
    --text-secondary: #b0b0c0;
    --text-muted: #707080;

    /* Border & Shadow */
    --border-color: rgba(255, 255, 255, 0.1);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
    --glow: 0 0 20px rgba(255, 107, 53, 0.3);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.5rem;
    --font-size-2xl: 2rem;
    --font-size-3xl: 2.5rem;

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;

    /* Z-Index */
    --z-modal: 1000;
    --z-toast: 2000;
    --z-nav: 100;
    --z-header: 90;
}

/* Reset & Base Styles */
html,
body {
    overflow-x: hidden;
    width: 100%;
    max-width: 100vw;
    overscroll-behavior: none;
}

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

body.modal-open {
    overflow: hidden;
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.active {
    display: block !important;
}

.flex {
    display: flex;
}

.flex-center {
    display: flex;
    justify-content: center;
    align-items: center;
}

/* Loading Screen */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--bg-primary);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    transition: opacity var(--transition-slow), visibility var(--transition-slow);
}

.loading-screen.hidden {
    opacity: 0;
    visibility: hidden;
}

.loading-content {
    text-align: center;
}

.loading-logo {
    font-size: 5rem;
    margin-bottom: var(--spacing-md);
    animation: pulse 2s ease-in-out infinite;
}

.loading-spinner {
    width: 40px;
    height: 40px;
    margin: var(--spacing-md) auto;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes pulse {

    0%,
    100% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.1);
    }
}

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

/* Screen Management */
.screen {
    display: none;
    min-height: 100vh;
}

.screen.active {
    display: flex;
    flex-direction: column;
}

/* Auth Screen */
.auth-container {
    max-width: 400px;
    width: 90%;
    margin: auto;
    padding: var(--spacing-lg);
}

.auth-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.logo {
    font-size: 4rem;
    margin-bottom: var(--spacing-sm);
    animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {

    0%,
    100% {
        transform: translateY(0);
    }

    50% {
        transform: translateY(-10px);
    }
}

.auth-header h1 {
    font-size: var(--font-size-2xl);
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.auth-header p {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

/* Auth Tabs */
.auth-tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.auth-tab {
    flex: 1;
    padding: var(--spacing-sm);
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: var(--font-size-base);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
}

.auth-tab.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    box-shadow: var(--glow);
}

/* Auth Forms */
.auth-form {
    display: none;
}

.auth-form.active {
    display: block;
}

.form-group {
    margin-bottom: var(--spacing-md);
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-secondary);
}

.form-group input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
    transition: all var(--transition-base);
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(255, 107, 53, 0.1);
}

.form-group input::placeholder {
    color: var(--text-muted);
}

/* Buttons */
.btn {
    width: 100%;
    padding: var(--spacing-md);
    border: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: 600;
    font-family: var(--font-family);
    cursor: pointer;
    transition: all var(--transition-base);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg), var(--glow);
}

.btn-primary:active {
    transform: translateY(0);
}

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

.btn-secondary:hover {
    background: var(--bg-tertiary);
    border-color: var(--primary);
}

.btn-danger {
    background: linear-gradient(135deg, #ff4757, #e84118);
    color: white;
}

.btn-danger:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.divider {
    text-align: center;
    margin: var(--spacing-lg) 0;
    color: var(--text-muted);
    font-size: var(--font-size-sm);
    position: relative;
}

.divider::before,
.divider::after {
    content: '';
    position: absolute;
    top: 50%;
    width: 40%;
    height: 1px;
    background: var(--border-color);
}

.divider::before {
    left: 0;
}

.divider::after {
    right: 0;
}

/* App Header */
.app-header {
    position: sticky;
    top: 0;
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md);
    z-index: var(--z-header);
}

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

#viewTitle {
    font-size: var(--font-size-xl);
    font-weight: 700;
}

.header-actions {
    display: flex;
    gap: var(--spacing-sm);
}

.icon-btn {
    width: 40px;
    height: 40px;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: var(--font-size-lg);
    cursor: pointer;
    transition: all var(--transition-base);
}

.icon-btn:hover {
    background: var(--bg-tertiary);
    transform: scale(1.05);
}

/* App Content */
.app-content {
    flex: 1;
    padding: var(--spacing-md);
    padding-bottom: calc(80px + var(--spacing-md));
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

/* Views */
.view {
    display: none;
    animation: fadeIn var(--transition-base);
}

.view.active {
    display: block;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.stat-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    transition: all var(--transition-base);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary);
}

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

.stat-info {
    flex: 1;
}

.stat-label {
    font-size: var(--font-size-xs);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.stat-value {
    font-size: var(--font-size-xl);
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Quick Actions */
.quick-actions {
    margin-bottom: var(--spacing-xl);
}

.quick-actions h2 {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-md);
}

.action-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: var(--spacing-md);
}

.action-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
    cursor: pointer;
    transition: all var(--transition-base);
}

.action-card:hover {
    transform: translateY(-4px);
    background: var(--bg-tertiary);
    border-color: var(--primary);
    box-shadow: var(--shadow-lg);
}

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

.action-label {
    font-size: var(--font-size-sm);
    font-weight: 600;
    text-align: center;
    color: var(--text-primary);
}

/* Activity List */
.recent-activity h2 {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-md);
}

.activity-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.activity-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

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

.activity-details {
    flex: 1;
}

.activity-title {
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.activity-time {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: var(--spacing-xl);
    color: var(--text-muted);
    font-size: var(--font-size-sm);
}

/* View Header */
.view-header {
    margin-bottom: var(--spacing-lg);
}

.view-actions {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.view-actions .btn {
    width: auto;
    flex: 1;
}

/* Nutrition */
.nutrition-header {
    margin-bottom: var(--spacing-lg);
}

.daily-goals h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-md);
}

.macro-bars {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.macro-bar-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-xs);
    font-size: var(--font-size-sm);
}

.progress-bar {
    height: 8px;
    background: var(--bg-glass);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: 4px;
    transition: width var(--transition-slow);
}

/* Leaderboard */
.exercise-tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    overflow-x: auto;
    padding-bottom: var(--spacing-xs);
}

.exercise-tab {
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 600;
    white-space: nowrap;
    cursor: pointer;
    transition: all var(--transition-base);
}

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

.leaderboard-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.leaderboard-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.leaderboard-rank {
    font-size: var(--font-size-2xl);
    font-weight: 800;
    width: 50px;
    text-align: center;
}

.leaderboard-rank.gold {
    color: #ffd700;
}

.leaderboard-rank.silver {
    color: #c0c0c0;
}

.leaderboard-rank.bronze {
    color: #cd7f32;
}

.leaderboard-info {
    flex: 1;
}

.leaderboard-name {
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.leaderboard-stats {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
}

.leaderboard-value {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--primary);
}

/* Profile */
.profile-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.profile-avatar {
    width: 100px;
    height: 100px;
    background: var(--bg-tertiary);
    border: 3px solid var(--primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    margin: 0 auto var(--spacing-md);
}

#profileName {
    font-size: var(--font-size-2xl);
    margin-bottom: var(--spacing-xs);
}

#profileEmail {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

.profile-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.profile-stat {
    text-align: center;
    padding: var(--spacing-md);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
}

.profile-stat h3 {
    font-size: var(--font-size-2xl);
    color: var(--primary);
    margin-bottom: var(--spacing-xs);
}

.profile-stat p {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
}

.profile-actions {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

/* Bottom Navigation */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xs) var(--spacing-sm);
    display: flex;
    justify-content: space-around;
    z-index: var(--z-nav);
    box-shadow: var(--shadow-lg);
}

.nav-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    padding: var(--spacing-xs);
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    transition: all var(--transition-base);
}

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

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

.nav-label {
    font-size: var(--font-size-xs);
    font-weight: 500;
}

/* Modal */
.modal-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(4px);
    z-index: var(--z-modal);
    padding: var(--spacing-md);
    overflow-y: auto;
}

.modal-overlay.active {
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    max-width: 500px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    overflow-x: hidden;
    animation: modalSlideIn var(--transition-base);
    scrollbar-width: none;
    -ms-overflow-style: none;
}

.modal::-webkit-scrollbar {
    display: none;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

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

.modal-title {
    font-size: var(--font-size-xl);
    font-weight: 700;
}

.modal-close {
    width: 32px;
    height: 32px;
    background: transparent;
    border: none;
    font-size: var(--font-size-xl);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-base);
}

.modal-close:hover {
    color: var(--primary);
    transform: rotate(90deg);
}

.modal-body {
    padding: var(--spacing-lg);
}

.modal-footer {
    padding: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: var(--spacing-sm);
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    top: var(--spacing-md);
    right: var(--spacing-md);
    z-index: var(--z-toast);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.toast {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    min-width: 250px;
    box-shadow: var(--shadow-lg);
    animation: toastSlideIn var(--transition-base);
}

@keyframes toastSlideIn {
    from {
        opacity: 0;
        transform: translateX(100%);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.toast.success {
    border-left: 4px solid #2ecc71;
}

.toast.error {
    border-left: 4px solid #e74c3c;
}

.toast.info {
    border-left: 4px solid var(--secondary);
}

/* List Container */
.list-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

/* Responsive Design */
@media (max-width: 768px) {
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .action-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    :root {
        --font-size-2xl: 1.75rem;
        --font-size-xl: 1.25rem;
    }

    .app-content {
        padding: var(--spacing-sm);
    }
}

/* PWA Specific */
@media (display-mode: standalone) {
    .app-header {
        padding-top: calc(env(safe-area-inset-top) + var(--spacing-md));
    }

    .bottom-nav {
        padding-bottom: calc(env(safe-area-inset-bottom) + var(--spacing-xs));
    }
}

/* Animations */
@keyframes slideUp {
    from {
        transform: translateY(100%);
        opacity: 0;
    }

    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.slide-up {
    animation: slideUp var(--transition-base);
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary);
}

/* Custom Select / Dropdown Styles */
select {
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
    background-color: var(--bg-glass);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm) var(--spacing-xl) var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23ff6b35' d='M6 9L1 4h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right var(--spacing-md) center;
    background-size: 12px;
}

select:hover {
    border-color: var(--primary);
    background-color: rgba(255, 107, 53, 0.05);
}

select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(255, 107, 53, 0.1);
}

select option {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    padding: var(--spacing-sm);
}

select:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}