/* ==============================================
   CSS VARIABLES & ROOT STYLES
   ============================================== */
:root {
    /* Light Theme Colors */
    --color-primary: #3b82f6;
    --color-primary-dark: #2563eb;
    --color-primary-light: #60a5fa;
    --color-secondary: #10b981;
    --color-accent: #f59e0b;
    
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-surface-hover: #f1f5f9;
    
    --color-text: #1e293b;
    --color-text-muted: #64748b;
    --color-text-light: #94a3b8;
    
    --color-border: #e2e8f0;
    --color-border-hover: #cbd5e1;
    
    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    --font-mono: 'Monaco', 'Courier New', monospace;
    
    /* Sizing */
    --container-width: 1200px;
    --converter-max-width: 600px;
    --border-radius: 0.75rem;
    --border-radius-sm: 0.5rem;
    
    /* Effects */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Theme */
[data-theme="dark"] {
    --color-bg: #0f172a;
    --color-surface: #1e293b;
    --color-surface-hover: #334155;
    
    --color-text: #f1f5f9;
    --color-text-muted: #94a3b8;
    --color-text-light: #64748b;
    
    --color-border: #334155;
    --color-border-hover: #475569;
    
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.5), 0 10px 10px -5px rgba(0, 0, 0, 0.3);
}

/* ==============================================
   RESET & BASE STYLES
   ============================================== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* ==============================================
   TYPOGRAPHY
   ============================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--color-primary-dark);
}

/* ==============================================
   LAYOUT COMPONENTS
   ============================================== */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* ==============================================
   HEADER
   ============================================== */
.header {
    background-color: var(--color-surface);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: var(--transition);
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md) var(--spacing-lg);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

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

.logo-text {
    font-size: 1.5rem;
    margin: 0;
    color: var(--color-text);
}

.nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-sm);
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-text);
    transition: var(--transition);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.nav-links a {
    color: var(--color-text-muted);
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-sm);
    transition: var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--color-primary);
    background-color: var(--color-surface-hover);
}

.theme-toggle {
    background: none;
    border: 2px solid var(--color-border);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    transition: var(--transition);
}

.theme-toggle:hover {
    border-color: var(--color-primary);
    transform: rotate(20deg);
}

/* ==============================================
   MAIN CONTENT
   ============================================== */
.main {
    min-height: calc(100vh - 200px);
    padding: var(--spacing-2xl) 0;
}

/* Hero Section */
.hero {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.hero-title {
    color: var(--color-text);
    margin-bottom: var(--spacing-md);
}

.hero-description {
    color: var(--color-text-muted);
    font-size: 1.125rem;
    max-width: 700px;
    margin: 0 auto;
}

/* Converter Section */
.converter-section {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-2xl);
}

.converter-card {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-lg);
    max-width: var(--converter-max-width);
    margin: 0 auto;
    width: 100%;
}

/* Rate Display */
.rate-display {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    margin-bottom: var(--spacing-xl);
    position: relative;
}

.rate-info {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xs);
}

.rate-label {
    font-size: 0.875rem;
    opacity: 0.9;
}

.rate-value {
    font-size: 1.5rem;
    font-weight: 700;
}

.rate-date {
    font-size: 0.875rem;
    opacity: 0.8;
}

.refresh-btn {
    position: absolute;
    top: var(--spacing-lg);
    right: var(--spacing-lg);
    background: rgba(255, 255, 255, 0.2);
    border: none;
    border-radius: 50%;
    width: 36px;
    height: 36px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    transition: var(--transition);
}

.refresh-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: rotate(180deg);
}

.refresh-btn:active {
    transform: rotate(360deg);
}

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

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

.input-label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text-muted);
}

.input-wrapper {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: var(--spacing-sm);
}

.input-field {
    flex: 1;
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    font-size: 1rem;
    background-color: var(--color-bg);
    color: var(--color-text);
    transition: var(--transition);
    font-family: var(--font-sans);
}

.input-field:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.result-field {
    font-weight: 600;
    background-color: var(--color-surface-hover);
}

.currency-select {
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    font-size: 1rem;
    background-color: var(--color-bg);
    color: var(--color-text);
    cursor: pointer;
    transition: var(--transition);
    min-width: 100px;
    font-family: var(--font-sans);
}

.currency-select:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

/* Swap Button */
.swap-container {
    display: flex;
    justify-content: center;
    margin: var(--spacing-sm) 0;
}

.swap-btn {
    background-color: var(--color-primary);
    color: white;
    border: none;
    border-radius: 50%;
    width: 48px;
    height: 48px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    transition: var(--transition);
    box-shadow: var(--shadow);
}

.swap-btn:hover {
    background-color: var(--color-primary-dark);
    transform: rotate(180deg) scale(1.1);
    box-shadow: var(--shadow-lg);
}

.swap-btn:active {
    transform: rotate(180deg) scale(0.95);
}

/* Copy Button */
.copy-btn {
    background-color: var(--color-secondary);
    color: white;
    border: none;
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    transition: var(--transition);
    margin-top: var(--spacing-md);
}

.copy-btn:hover {
    background-color: #059669;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

/* Status Message */
.status-message {
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-sm);
    font-size: 0.875rem;
    text-align: center;
    display: none;
}

.status-message.success {
    background-color: rgba(16, 185, 129, 0.1);
    color: var(--color-success);
    border: 1px solid var(--color-success);
    display: block;
}

.status-message.error {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--color-error);
    border: 1px solid var(--color-error);
    display: block;
}

/* History Section */
.history-section {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow);
}

.history-title {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
}

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

.history-item {
    padding: var(--spacing-md);
    background-color: var(--color-bg);
    border-radius: var(--border-radius-sm);
    border-left: 3px solid var(--color-primary);
    font-size: 0.875rem;
}

.history-empty {
    text-align: center;
    color: var(--color-text-muted);
    padding: var(--spacing-lg);
}

.clear-history-btn {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: transparent;
    border: 2px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    color: var(--color-text-muted);
    font-size: 0.875rem;
    cursor: pointer;
    transition: var(--transition);
}

.clear-history-btn:hover {
    border-color: var(--color-error);
    color: var(--color-error);
}

/* ==============================================
   SECTIONS
   ============================================== */
.section-title {
    text-align: center;
    margin-bottom: var(--spacing-md);
}

.section-description {
    text-align: center;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Currencies Section */
.currencies-section {
    margin-bottom: var(--spacing-2xl);
}

.currencies-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--spacing-md);
}

.currency-item {
    background-color: var(--color-surface);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-sm);
    text-align: center;
    border: 2px solid var(--color-border);
    transition: var(--transition);
}

.currency-item:hover {
    border-color: var(--color-primary);
    box-shadow: var(--shadow);
    transform: translateY(-2px);
}

.currency-code {
    font-weight: 700;
    font-size: 1.125rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
}

.currency-name {
    font-size: 0.875rem;
    color: var(--color-text-muted);
}

/* FAQ Section */
.faq-section {
    margin-bottom: var(--spacing-2xl);
}

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

.faq-item {
    background-color: var(--color-surface);
    border-radius: var(--border-radius-sm);
    margin-bottom: var(--spacing-md);
    box-shadow: var(--shadow);
}

.faq-question {
    padding: var(--spacing-lg);
    font-weight: 600;
    cursor: pointer;
    list-style: none;
    user-select: none;
    transition: var(--transition);
}

.faq-question::-webkit-details-marker {
    display: none;
}

.faq-question::before {
    content: '+';
    margin-right: var(--spacing-md);
    font-size: 1.5rem;
    color: var(--color-primary);
    transition: var(--transition);
}

.faq-item[open] .faq-question::before {
    content: '−';
}

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

.faq-answer {
    padding: 0 var(--spacing-lg) var(--spacing-lg) var(--spacing-lg);
    color: var(--color-text-muted);
    line-height: 1.6;
}

/* Privacy Section */
.privacy-section {
    margin-bottom: var(--spacing-2xl);
}

.privacy-content {
    max-width: 800px;
    margin: 0 auto;
    background-color: var(--color-surface);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.privacy-content p {
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.privacy-content strong {
    color: var(--color-primary);
}

/* ==============================================
   FOOTER
   ============================================== */
.footer {
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
    text-align: center;
}

.footer-disclaimer {
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

.footer-disclaimer p {
    margin-bottom: var(--spacing-sm);
}

.footer-update {
    font-weight: 600;
    color: var(--color-text);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    flex-wrap: wrap;
}

.footer-links a {
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

.footer-links a:hover {
    color: var(--color-primary);
}

.footer-copy {
    color: var(--color-text-light);
    font-size: 0.875rem;
}

/* ==============================================
   BACK TO TOP BUTTON
   ============================================== */
.back-to-top {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
    background-color: var(--color-primary);
    color: white;
    border: none;
    border-radius: 50%;
    width: 48px;
    height: 48px;
    font-size: 1.5rem;
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    z-index: 999;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
}

/* ==============================================
   RESPONSIVE DESIGN
   ============================================== */
@media (max-width: 768px) {
    html {
        font-size: 14px;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--color-surface);
        flex-direction: column;
        padding: var(--spacing-lg);
        box-shadow: var(--shadow-lg);
    }
    
    .nav-links.active {
        display: flex;
    }
    
    .hero-title {
        font-size: 1.75rem;
    }
    
    .converter-card {
        padding: var(--spacing-lg);
    }
    
    .input-wrapper {
        grid-template-columns: 1fr;
    }
    
    .currency-select {
        width: 100%;
    }
    
    .currencies-grid {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    }
    
    .back-to-top {
        bottom: var(--spacing-lg);
        right: var(--spacing-lg);
        width: 40px;
        height: 40px;
    }
}

@media (min-width: 769px) {
    .converter-section {
        grid-template-columns: 1fr 400px;
    }
}

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

@keyframes spin {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

.animate-in {
    animation: fadeIn 0.5s ease-out;
}

.spinning {
    animation: spin 1s linear infinite;
}

/* ==============================================
   UTILITY CLASSES
   ============================================== */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* ==============================================
   ACCESSIBILITY
   ============================================== */
:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

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

/* ==============================================
   PRINT STYLES
   ============================================== */
@media print {
    .header,
    .footer,
    .back-to-top,
    .theme-toggle,
    .refresh-btn,
    .copy-btn,
    .history-section {
        display: none;
    }
    
    .converter-card {
        box-shadow: none;
        border: 1px solid #000;
    }
}