/**
 * Scientific Calculator - Stylesheet
 * Mobile-first responsive design
 */

/* ========== CSS Variables ========== */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    --secondary-color: #10b981;
    --accent-color: #f59e0b;
    --error-color: #ef4444;
    
    --bg-color: #f8fafc;
    --bg-light: #ffffff;
    --bg-dark: #1e293b;
    
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'Roboto Mono', 'Courier New', monospace;
    
    --transition: all 0.3s ease;
    --border-radius: 12px;
    --border-radius-sm: 8px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    color: var(--text-primary);
    background-color: var(--bg-color);
    line-height: 1.6;
    overflow-x: hidden;
    opacity: 0;
    transition: opacity 0.3s ease;
}

body.loaded {
    opacity: 1;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ========== Header ========== */
.header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--bg-light);
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
}

.logo i {
    font-size: 1.75rem;
}

.nav-menu {
    position: relative;
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0.5rem;
}

.nav-list {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

.nav-list a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
    padding: 0.5rem 0;
}

.nav-list a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
}

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

.nav-list a:hover::after,
.nav-list a.active::after {
    width: 100%;
}

/* ========== Hero Section ========== */
.hero {
    text-align: center;
    padding: 3rem 0 2rem;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary-color) 100%);
    color: white;
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.125rem;
    opacity: 0.95;
    max-width: 600px;
    margin: 0 auto;
}

/* ========== Calculator Section ========== */
.calculator-section {
    padding: 3rem 0;
}

.calculator-wrapper {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    max-width: 600px;
    margin: 0 auto;
}

.calculator {
    background: var(--bg-light);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-xl);
    padding: 1.5rem;
    position: relative;
}

/* Display */
.display-container {
    background: linear-gradient(135deg, #1e293b 0%, #334155 100%);
    border-radius: var(--border-radius-sm);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    min-height: 120px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

.expression {
    font-family: var(--font-mono);
    font-size: 1rem;
    color: #94a3b8;
    min-height: 24px;
    text-align: right;
    word-wrap: break-word;
    margin-bottom: 0.5rem;
}

.display {
    font-family: var(--font-mono);
    font-size: 2.5rem;
    color: white;
    text-align: right;
    word-wrap: break-word;
    font-weight: 500;
}

/* Buttons */
.buttons {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.button-row {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 0.5rem;
}

.btn {
    position: relative;
    padding: 1rem;
    font-size: 1rem;
    font-weight: 500;
    border: none;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: var(--transition);
    font-family: var(--font-main);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    user-select: none;
}

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

.btn-number {
    background: white;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

.btn-operator {
    background: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
    color: white;
}

.btn-operator:hover {
    background: linear-gradient(135deg, #2563eb 0%, #1e40af 100%);
    box-shadow: var(--shadow-md);
}

.btn-function {
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    color: var(--text-primary);
    font-size: 0.875rem;
    border: 1px solid var(--border-color);
}

.btn-function:hover {
    background: linear-gradient(135deg, #e2e8f0 0%, #cbd5e1 100%);
    border-color: var(--primary-light);
}

.btn-function.active {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    border-color: var(--primary-color);
}

.btn-equals {
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
    color: white;
    font-size: 1.25rem;
}

.btn-equals:hover {
    background: linear-gradient(135deg, #059669 0%, #047857 100%);
    box-shadow: var(--shadow-md);
}

/* Ripple Effect */
.ripple {
    position: absolute;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.5);
    transform: scale(0);
    animation: ripple-animation 0.6s ease-out;
    pointer-events: none;
}

@keyframes ripple-animation {
    to {
        transform: scale(4);
        opacity: 0;
    }
}

/* Mode Indicator */
.mode-indicator {
    position: absolute;
    top: 1rem;
    left: 1rem;
    background: rgba(37, 99, 235, 0.1);
    padding: 0.375rem 0.75rem;
    border-radius: 6px;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--primary-color);
    z-index: 10;
}

/* History Panel */
.history-panel {
    background: var(--bg-color);
    border-radius: var(--border-radius-sm);
    padding: 1rem;
    margin-top: 1rem;
    max-height: 300px;
    overflow-y: auto;
    border: 1px solid var(--border-color);
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 2px solid var(--border-color);
}

.history-header h3 {
    font-size: 1rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin: 0;
}

.history-header i {
    color: var(--primary-color);
}

.btn-clear-history {
    background: transparent;
    border: none;
    color: var(--text-light);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 6px;
    transition: var(--transition);
    font-size: 0.9rem;
}

.btn-clear-history:hover {
    background: rgba(239, 68, 68, 0.1);
    color: var(--error-color);
}

.history-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.history-empty {
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-light);
}

.history-empty i {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    opacity: 0.5;
}

.history-empty p {
    margin: 0;
    font-size: 0.875rem;
}

.history-item {
    background: white;
    padding: 0.75rem;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    cursor: pointer;
    transition: var(--transition);
    animation: slideIn 0.3s ease-out;
}

.history-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-sm);
    transform: translateX(4px);
}

.history-expression {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.history-result {
    font-family: var(--font-mono);
    font-size: 1rem;
    color: var(--text-primary);
    font-weight: 600;
}

.history-time {
    font-size: 0.75rem;
    color: var(--text-light);
    margin-top: 0.25rem;
}

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

/* Custom Scrollbar for History */
.history-list::-webkit-scrollbar {
    width: 6px;
}

.history-list::-webkit-scrollbar-track {
    background: var(--bg-color);
    border-radius: 3px;
}

.history-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

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

/* ========== Ad Containers ========== */
.ad-container {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 2rem 0;
    padding: 1rem;
}

.ad-placeholder {
    text-align: center;
}

.ad-label {
    font-size: 0.75rem;
    color: var(--text-light);
    text-transform: uppercase;
    margin-bottom: 0.5rem;
    letter-spacing: 0.5px;
}

.ad-space {
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    border: 2px dashed var(--border-color);
    border-radius: var(--border-radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
    font-size: 0.875rem;
    font-weight: 500;
}

.ad-horizontal {
    width: 728px;
    max-width: 100%;
    height: 90px;
}

.ad-vertical {
    width: 300px;
    height: 600px;
}

.ad-side {
    display: none;
}

/* ========== User Guide Section ========== */
.user-guide-section {
    padding: 4rem 0;
    background: white;
}

.user-guide-section h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.section-intro {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 3rem;
}

.guide-content {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    margin-top: 2rem;
}

.guide-card {
    background: var(--bg-light);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: var(--transition);
    opacity: 0;
    transform: translateY(20px);
}

.guide-card.animate-in {
    opacity: 1;
    transform: translateY(0);
}

.guide-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.guide-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary-color) 100%);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.5rem;
}

.guide-icon i {
    font-size: 1.75rem;
    color: white;
}

.guide-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.guide-card ul {
    list-style: none;
    padding-left: 0;
}

.guide-card li {
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
    color: var(--text-secondary);
    line-height: 1.7;
}

.guide-card li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

.guide-card li strong {
    color: var(--text-primary);
    font-weight: 600;
}

.guide-note {
    background: #eff6ff;
    border-left: 4px solid var(--primary-color);
    padding: 1rem;
    margin-top: 1rem;
    border-radius: 6px;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
}

.guide-note i {
    color: var(--primary-color);
    margin-top: 0.25rem;
}

.guide-note span {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Examples Grid */
.guide-examples {
    grid-column: 1 / -1;
}

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.example {
    background: var(--bg-color);
    padding: 1.5rem;
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
}

.example strong {
    display: block;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    font-size: 1rem;
}

.example code {
    display: block;
    background: white;
    padding: 0.75rem;
    border-radius: 6px;
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-primary);
    margin: 0.5rem 0;
    border: 1px solid var(--border-color);
}

.example span {
    display: block;
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-top: 0.5rem;
}

/* ========== Features Section ========== */
.features-section {
    padding: 4rem 0;
    background: var(--bg-color);
}

.features-section h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--text-primary);
}

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

.feature-card {
    background: white;
    padding: 2rem;
    border-radius: var(--border-radius);
    text-align: center;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: var(--transition);
    opacity: 0;
    transform: translateY(20px);
}

.feature-card.animate-in {
    opacity: 1;
    transform: translateY(0);
}

.feature-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.feature-card i {
    font-size: 3rem;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ========== Footer ========== */
.footer {
    background: #1e293b;
    color: #e2e8f0;
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}

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

.footer-section h3 {
    color: white;
    margin-bottom: 1rem;
    font-size: 1.125rem;
}

.footer-section p {
    color: #cbd5e1;
    line-height: 1.7;
    font-size: 0.9rem;
}

.footer-section ul {
    list-style: none;
    padding: 0;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: #cbd5e1;
    text-decoration: none;
    transition: var(--transition);
    display: inline-block;
}

.footer-section a:hover {
    color: var(--primary-light);
    transform: translateX(4px);
}

.footer-bottom {
    padding-top: 2rem;
    border-top: 1px solid #334155;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.footer-bottom p {
    color: #94a3b8;
    font-size: 0.875rem;
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: #334155;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    transition: var(--transition);
    text-decoration: none;
}

.social-links a:hover {
    background: var(--primary-color);
    transform: translateY(-4px);
}

/* ========== Responsive Design ========== */
@media (max-width: 768px) {
    /* Mobile menu */
    .menu-toggle {
        display: block;
    }

    .nav-list {
        position: absolute;
        top: 100%;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 1rem;
        box-shadow: var(--shadow-lg);
        border-radius: var(--border-radius-sm);
        min-width: 200px;
        opacity: 0;
        visibility: hidden;
        transform: translateY(-10px);
        transition: var(--transition);
    }

    .nav-list.active {
        opacity: 1;
        visibility: visible;
        transform: translateY(0);
    }

    /* Hero */
    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

    /* Calculator */
    .display {
        font-size: 2rem;
    }

    .button-row {
        gap: 0.375rem;
    }

    .btn {
        padding: 0.875rem 0.5rem;
        font-size: 0.875rem;
    }

    .btn-function {
        font-size: 0.75rem;
    }

    /* Sections */
    .user-guide-section h2,
    .features-section h2 {
        font-size: 2rem;
    }

    .guide-content {
        gap: 1.5rem;
    }

    /* Footer */
    .footer-bottom {
        flex-direction: column;
        text-align: center;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    .calculator-wrapper {
        max-width: 800px;
        grid-template-columns: 1fr 300px;
    }

    .ad-side {
        display: block;
    }
}

@media (min-width: 1025px) {
    .calculator-wrapper {
        max-width: 1000px;
        grid-template-columns: 1fr 300px;
    }

    .ad-side {
        display: block;
    }

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

/* ========== Print Styles ========== */
@media print {
    .header,
    .footer,
    .ad-container,
    .menu-toggle {
        display: none;
    }

    body {
        background: white;
    }

    .calculator {
        box-shadow: none;
        border: 1px solid #ccc;
    }
}

/* ========== Accessibility ========== */
@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 keyboard navigation */
button:focus-visible,
a:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}