/* CSS Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Palette */
    --primary-color: #05386B;
    --secondary-color: #379683;
    --accent-color: #5CDB95;
    --light-accent: #8EE4AF;
    --background-light: #EDF5E1;
    
    /* Dark Mode Colors */
    --dark-bg: #1a1a1a;
    --dark-surface: #2d2d2d;
    --dark-text: #e0e0e0;
    --dark-border: #404040;
    
    /* Typography */
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-size-base: 16px;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.5rem;
    --font-size-2xl: 2rem;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Borders */
    --border-radius: 8px;
    --border-radius-lg: 12px;
    --border-width: 1px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* Light Theme (Default) */
body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--primary-color);
    background: linear-gradient(135deg, var(--background-light) 0%, #f8fffe 100%);
    min-height: 100vh;
    transition: all var(--transition-normal);
}

/* Dark Theme */
body.dark-theme {
    color: var(--dark-text);
    background: linear-gradient(135deg, var(--dark-bg) 0%, #2a2a2a 100%);
}

.dark-theme .card,
.dark-theme .modal-content {
    background: var(--dark-surface);
    border-color: var(--dark-border);
}

.dark-theme .form-input,
.dark-theme .btn {
    background: var(--dark-surface);
    border-color: var(--dark-border);
    color: var(--dark-text);
}

.dark-theme .form-input:focus {
    border-color: var(--accent-color);
}

.dark-theme .tab-btn.active {
    background: var(--secondary-color);
    color: white;
}

/* App Container */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    background: var(--primary-color);
    color: white;
    padding: var(--spacing-lg) var(--spacing-md);
    box-shadow: var(--shadow-md);
}

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

.app-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

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

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

.theme-toggle,
.history-toggle {
    background: rgba(255, 255, 255, 0.1);
    border: none;
    color: white;
    padding: var(--spacing-sm);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: 1.2rem;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover,
.history-toggle:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: scale(1.05);
}

/* Main Content */
.main-content {
    flex: 1;
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md);
    width: 100%;
}

/* Tab Navigation */
.tab-navigation {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
    border-bottom: 2px solid var(--light-accent);
    overflow-x: auto;
}

.tab-btn {
    background: transparent;
    border: none;
    padding: var(--spacing-md) var(--spacing-lg);
    cursor: pointer;
    font-size: var(--font-size-base);
    color: var(--secondary-color);
    border-radius: var(--border-radius) var(--border-radius) 0 0;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    white-space: nowrap;
    min-width: fit-content;
}

.tab-btn:hover {
    background: rgba(92, 219, 149, 0.1);
}

.tab-btn.active {
    background: var(--accent-color);
    color: var(--primary-color);
    font-weight: 600;
}

.tab-icon {
    font-size: 1.1rem;
}

/* Tab Content */
.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn var(--transition-normal);
}

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

/* Cards */
.card {
    background: white;
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-lg);
    border: var(--border-width) solid var(--light-accent);
    transition: all var(--transition-normal);
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 25px rgba(0, 0, 0, 0.15);
}

.card-title {
    font-size: var(--font-size-xl);
    color: var(--primary-color);
    margin-bottom: var(--spacing-lg);
    text-align: center;
    font-weight: 600;
}

/* Forms */
.form {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

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

.form-label {
    font-weight: 600;
    color: var(--primary-color);
    font-size: var(--font-size-base);
}

.form-input {
    padding: var(--spacing-md);
    border: 2px solid var(--light-accent);
    border-radius: var(--border-radius);
    font-size: var(--font-size-base);
    transition: all var(--transition-fast);
    background: white;
}

.form-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(92, 219, 149, 0.1);
}

.form-input:invalid {
    border-color: #ef4444;
}

.form-help {
    color: var(--secondary-color);
    font-size: 0.875rem;
    font-style: italic;
}

/* Buttons */
.btn {
    padding: var(--spacing-md) var(--spacing-lg);
    border: none;
    border-radius: var(--border-radius);
    font-size: var(--font-size-base);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    text-decoration: none;
    min-height: 48px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-color) 0%, var(--secondary-color) 100%);
    color: var(--primary-color);
}

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

.btn-secondary {
    background: var(--light-accent);
    color: var(--primary-color);
}

.btn-secondary:hover {
    background: var(--accent-color);
}

.btn-icon {
    font-size: 1.1rem;
}

/* Results */
.results {
    margin-top: var(--spacing-xl);
    padding: var(--spacing-lg);
    background: linear-gradient(135deg, var(--background-light) 0%, rgba(92, 219, 149, 0.1) 100%);
    border-radius: var(--border-radius);
    border: 2px solid var(--light-accent);
}

.results-title {
    font-size: var(--font-size-lg);
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
    text-align: center;
    font-weight: 600;
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.result-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: white;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.result-label {
    font-weight: 600;
    color: var(--secondary-color);
}

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

/* Trip Estimator */
.trip-estimator {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    background: white;
    border-radius: var(--border-radius);
    border: 2px solid var(--accent-color);
}

.estimator-title {
    font-size: var(--font-size-lg);
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
    text-align: center;
}

.estimate-result {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: var(--background-light);
    border-radius: var(--border-radius);
    margin-top: var(--spacing-md);
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: var(--spacing-md);
}

.modal-content {
    background: white;
    border-radius: var(--border-radius-lg);
    max-width: 800px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg);
    border-bottom: 2px solid var(--light-accent);
}

.modal-title {
    font-size: var(--font-size-xl);
    color: var(--primary-color);
    font-weight: 600;
}

.modal-close {
    background: none;
    border: none;
    font-size: 2rem;
    color: var(--secondary-color);
    cursor: pointer;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--light-accent);
    color: var(--primary-color);
}

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

/* Graph Container */
.graph-container {
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-lg);
    background: var(--background-light);
    border-radius: var(--border-radius);
    text-align: center;
}

#consumptionChart {
    max-width: 100%;
    height: auto;
}

/* History */
.history-section {
    margin-bottom: var(--spacing-lg);
}

.history-title {
    font-size: var(--font-size-lg);
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
    font-weight: 600;
}

.history-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    max-height: 300px;
    overflow-y: auto;
}

.history-item {
    padding: var(--spacing-md);
    background: white;
    border: 2px solid var(--light-accent);
    border-radius: var(--border-radius);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--spacing-sm);
    transition: all var(--transition-fast);
}

.history-item:hover {
    border-color: var(--accent-color);
    transform: translateX(5px);
}

.history-detail {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
}

.history-label {
    font-size: 0.875rem;
    color: var(--secondary-color);
    font-weight: 600;
}

.history-value {
    font-weight: 700;
    color: var(--primary-color);
}

.history-date {
    grid-column: 1 / -1;
    text-align: center;
    font-size: 0.875rem;
    color: var(--secondary-color);
    font-style: italic;
    border-top: 1px solid var(--light-accent);
    padding-top: var(--spacing-sm);
    margin-top: var(--spacing-sm);
}

.no-history {
    text-align: center;
    color: var(--secondary-color);
    font-style: italic;
    padding: var(--spacing-xl);
}

.history-actions {
    text-align: center;
}

/* Loading Indicator */
.loading {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 255, 255, 0.9);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

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

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

/* Footer */
.footer {
    background: var(--primary-color);
    color: white;
    text-align: center;
    padding: var(--spacing-lg);
    margin-top: auto;
}

.footer-text {
    font-size: 0.875rem;
}

.footer-text a {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 600;
}

.footer-text a:hover {
    text-decoration: underline;
}

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

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Responsive Design */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: var(--spacing-md);
        text-align: center;
    }

    .app-title {
        font-size: var(--font-size-xl);
    }

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

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

    .tab-navigation {
        flex-direction: column;
    }

    .tab-btn {
        justify-content: center;
        padding: var(--spacing-md);
    }

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

    .result-item {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-xs);
    }

    .estimate-result {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-xs);
    }

    .modal-content {
        margin: var(--spacing-sm);
        max-height: calc(100vh - 2rem);
    }

    .history-item {
        grid-template-columns: 1fr;
    }

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

@media (max-width: 480px) {
    .form-input,
    .btn {
        font-size: 16px; /* Prevents zoom on iOS */
    }

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

    .modal-header,
    .modal-body {
        padding: var(--spacing-md);
    }
}

/* Print Styles */
@media print {
    .header-controls,
    .tab-navigation,
    .btn,
    .modal {
        display: none !important;
    }

    .card {
        box-shadow: none;
        border: 2px solid var(--primary-color);
    }

    body {
        background: white !important;
    }
}

/* High Contrast Mode */
@media (prefers-contrast: high) {
    :root {
        --accent-color: #00ff00;
        --secondary-color: #0066cc;
    }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus Styles for Accessibility */
button:focus,
input:focus,
a:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

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

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

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

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