/* ==================== */
/* Reset & Global Styles */
/* ==================== */

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

:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #ec4899;
    --accent-color: #14b8a6;
    --bg-color: #ffffff;
    --bg-alternate: #f8fafc;
    --text-color: #1e293b;
    --text-light: #64748b;
    --border-color: #e2e8f0;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.2);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Poppins', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* ==================== */
/* Navigation */
/* ==================== */

.navbar {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    padding: 1.2rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 4px 20px rgba(99, 102, 241, 0.3);
    backdrop-filter: blur(10px);
}

.nav-container {
    max-width: 1600px;
    margin: 0 auto;
    padding: 0 25px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.3rem;
    font-weight: 700;
    white-space: nowrap;
    min-width: auto;
    flex-shrink: 0;
}

.logo-text {
    white-space: nowrap;
}

.logo-icon {
    font-size: 1.8rem;
    animation: pulse 2s infinite;
    flex-shrink: 0;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 0.4rem;
    flex-wrap: nowrap;
    align-items: center;
}

.nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 0.6rem 0.9rem;
    border-radius: 10px;
    transition: var(--transition);
    position: relative;
    font-size: 0.9rem;
    white-space: nowrap;
}

.nav-link::before {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 3px;
    background: white;
    transition: var(--transition);
    transform: translateX(-50%);
    border-radius: 3px;
}

.nav-link:hover::before,
.nav-link.active::before {
    width: 80%;
}

.nav-link:hover,
.nav-link.active {
    background: rgba(255, 255, 255, 0.15);
    transform: translateY(-2px);
}

.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
}

.menu-toggle span {
    width: 25px;
    height: 3px;
    background: white;
    border-radius: 3px;
    transition: var(--transition);
}

/* ==================== */
/* Hero Section */
/* ==================== */

.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);
    color: white;
    padding: 140px 20px 120px;
    position: relative;
    overflow: hidden;
    min-height: 75vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1440 320"><path fill="%23ffffff" fill-opacity="0.1" d="M0,96L48,112C96,128,192,160,288,160C384,160,480,128,576,122.7C672,117,768,139,864,144C960,149,1056,139,1152,128C1248,117,1344,107,1392,101.3L1440,96L1440,320L1392,320C1344,320,1248,320,1152,320C1056,320,960,320,864,320C768,320,672,320,576,320C480,320,384,320,288,320C192,320,96,320,48,320L0,320Z"></path></svg>') no-repeat bottom;
    background-size: cover;
    animation: wave 10s linear infinite;
}

@keyframes wave {
    0% { transform: translateX(0); }
    100% { transform: translateX(-50%); }
}

.hero-content {
    text-align: center;
    max-width: 800px;
    position: relative;
    z-index: 1;
}

.hero-title {
    font-size: 4rem;
    font-weight: 800;
    margin-bottom: 1.5rem;
    animation: fadeInUp 1s ease;
    text-shadow: 2px 2px 20px rgba(0, 0, 0, 0.2);
    line-height: 1.2;
}

.hero-subtitle {
    font-size: 1.4rem;
    margin-bottom: 2.5rem;
    opacity: 0.95;
    animation: fadeInUp 1s ease 0.2s backwards;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    line-height: 1.8;
}

.cta-button {
    background: white;
    color: var(--primary-color);
    padding: 1.2rem 3.5rem;
    border: none;
    border-radius: 50px;
    font-size: 1.2rem;
    font-weight: 700;
    cursor: pointer;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    transition: var(--transition);
    animation: fadeInUp 1s ease 0.4s backwards;
    position: relative;
    overflow: hidden;
}

.cta-button::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(99, 102, 241, 0.1);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.cta-button:hover::before {
    width: 300px;
    height: 300px;
}

.cta-button:hover {
    transform: translateY(-5px) scale(1.05);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.4);
}

.hero-animation {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
}

.floating-stat {
    position: absolute;
    font-size: 3rem;
    font-weight: 700;
    opacity: 0.2;
    animation: float 6s ease-in-out infinite;
}

.floating-stat:nth-child(2) { animation-delay: 1s; }
.floating-stat:nth-child(3) { animation-delay: 2s; }
.floating-stat:nth-child(4) { animation-delay: 3s; }
.floating-stat:nth-child(5) { animation-delay: 4s; }

@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-30px); }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== */
/* Sections */
/* ==================== */

.section {
    padding: 80px 20px;
}

.bg-alternate {
    background-color: var(--bg-alternate);
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--primary-color);
    position: relative;
    display: inline-block;
    width: 100%;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 100px;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    border-radius: 2px;
}

/* ==================== */
/* Content Cards */
/* ==================== */

.content-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.content-card {
    background: white;
    padding: 2.5rem;
    border-radius: 24px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.content-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 5px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color), var(--accent-color));
    transform: translateY(-5px);
    transition: var(--transition);
}

.content-card:hover::before {
    transform: translateY(0);
}

.content-card:hover {
    transform: translateY(-12px);
    box-shadow: 0 12px 40px rgba(99, 102, 241, 0.2);
    border-color: var(--primary-light);
}

.card-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

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

.content-card p {
    color: var(--text-light);
    line-height: 1.8;
}

/* ==================== */
/* Info & Theory Boxes */
/* ==================== */

.info-box {
    background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
    color: white;
    padding: 2rem;
    border-radius: 15px;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-md);
}

.intro-text {
    font-size: 1.2rem;
    line-height: 1.8;
    margin: 0;
}

.theory-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    border-left: 5px solid var(--primary-color);
    margin-top: 2rem;
}

.theory-box h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    font-size: 1.8rem;
}

.concept-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.concept-item {
    background: var(--bg-alternate);
    padding: 1.5rem;
    border-radius: 10px;
    border-left: 4px solid var(--accent-color);
    transition: var(--transition);
}

.concept-item:hover {
    transform: translateX(5px);
    background: #e0f2fe;
}

.concept-item strong {
    color: var(--primary-color);
}

/* ==================== */
/* Steps Container */
/* ==================== */

.steps-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin: 3rem 0;
}

.step-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    position: relative;
    transition: var(--transition);
}

.step-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.step-number {
    position: absolute;
    top: -20px;
    left: 20px;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    box-shadow: var(--shadow-md);
}

.step-card h3 {
    margin-top: 1.5rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
    font-size: 1.3rem;
}

.step-card p {
    color: var(--text-light);
    line-height: 1.8;
    margin-bottom: 0.5rem;
}

.step-card strong {
    color: var(--text-color);
}

/* ==================== */
/* Error Types */
/* ==================== */

.error-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 1.5rem;
}

.error-card {
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.error-card:hover {
    transform: scale(1.05);
}

.error-card.type1 {
    background: linear-gradient(135deg, #fee2e2, #fca5a5);
}

.error-card.type2 {
    background: linear-gradient(135deg, #dbeafe, #93c5fd);
}

.error-card h4 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.error-example {
    margin-top: 1rem;
    font-style: italic;
    color: var(--text-color);
    opacity: 0.8;
}

/* ==================== */
/* P-Value Scale */
/* ==================== */

.interactive-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    margin-top: 2rem;
}

.interactive-box h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.p-value-scale {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-top: 2rem;
}

.p-value-marker {
    padding: 1.5rem;
    border-radius: 10px;
    text-align: center;
    font-weight: 600;
    transition: var(--transition);
    cursor: pointer;
}

.p-value-marker:nth-child(1) {
    background: linear-gradient(135deg, #10b981, #059669);
    color: white;
}

.p-value-marker:nth-child(2) {
    background: linear-gradient(135deg, #3b82f6, #2563eb);
    color: white;
}

.p-value-marker:nth-child(3) {
    background: linear-gradient(135deg, #f59e0b, #d97706);
    color: white;
}

.p-value-marker:nth-child(4) {
    background: linear-gradient(135deg, #ef4444, #dc2626);
    color: white;
}

.p-value-marker:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.p-value-marker span {
    display: block;
    font-size: 0.9rem;
    margin-top: 0.5rem;
    opacity: 0.9;
}

/* ==================== */
/* Formula Box */
/* ==================== */

.formula-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    margin: 2rem 0;
}

.formula-box h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.formula {
    background: var(--bg-alternate);
    padding: 1.5rem;
    border-radius: 10px;
    text-align: center;
    font-size: 1.3rem;
    font-weight: 500;
    margin: 1rem 0;
    border: 2px solid var(--primary-light);
    font-family: 'Courier New', monospace;
}

.formula-explanation {
    margin-top: 2rem;
}

.formula-explanation p {
    color: var(--text-color);
    margin-bottom: 0.5rem;
    font-weight: 600;
}

/* ==================== */
/* Confidence Levels */
/* ==================== */

.confidence-levels {
    margin: 3rem 0;
}

.confidence-levels h3 {
    color: var(--primary-color);
    margin-bottom: 2rem;
    text-align: center;
}

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

.level-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    text-align: center;
    transition: var(--transition);
    border: 3px solid transparent;
}

.level-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.level-card.featured {
    border-color: var(--primary-color);
    background: linear-gradient(135deg, #f0f9ff, #e0f2fe);
}

.level-percent {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.level-desc {
    color: var(--text-light);
    margin-top: 1rem;
}

/* ==================== */
/* Interpretation Box */
/* ==================== */

.interpretation-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    margin: 2rem 0;
}

.interpretation-box h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.interpretation-content {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.correct {
    background: linear-gradient(135deg, #d1fae5, #a7f3d0);
    padding: 1.5rem;
    border-radius: 10px;
    border-left: 5px solid var(--success-color);
}

.incorrect {
    background: linear-gradient(135deg, #fee2e2, #fecaca);
    padding: 1.5rem;
    border-radius: 10px;
    border-left: 5px solid var(--error-color);
}

.note {
    background: var(--bg-alternate);
    padding: 1.5rem;
    border-radius: 10px;
    color: var(--text-light);
    font-style: italic;
    border-left: 5px solid var(--primary-color);
}

/* ==================== */
/* Test Cards */
/* ==================== */

.test-category {
    margin: 3rem 0;
}

.category-title {
    color: var(--primary-color);
    font-size: 2rem;
    margin-bottom: 2rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid var(--primary-light);
}

.test-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.test-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border-top: 4px solid var(--primary-color);
}

.test-card.single {
    max-width: 100%;
}

.test-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
    border-top-color: var(--secondary-color);
}

.test-card h4 {
    color: var(--primary-color);
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.test-purpose {
    color: var(--text-light);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.test-formula {
    background: var(--bg-alternate);
    padding: 1rem;
    border-radius: 8px;
    text-align: center;
    font-family: 'Courier New', monospace;
    font-size: 1.2rem;
    margin: 1.5rem 0;
    border: 2px solid var(--border-color);
}

.test-example {
    margin-top: 1rem;
    padding: 1rem;
    background: #fef3c7;
    border-radius: 8px;
    border-left: 4px solid var(--warning-color);
}

/* ==================== */
/* ANOVA */
/* ==================== */

.anova-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
}

.anova-components {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.component {
    background: var(--bg-alternate);
    padding: 1.5rem;
    border-radius: 10px;
    border-left: 4px solid var(--accent-color);
}

/* ==================== */
/* Regression */
/* ==================== */

.regression-types {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.regression-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    border-top: 4px solid var(--accent-color);
}

.regression-card h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.formula-parts {
    margin-top: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.formula-parts p {
    padding: 0.5rem;
    background: var(--bg-alternate);
    border-radius: 5px;
}

.formula-desc {
    margin-top: 1rem;
    color: var(--text-light);
    line-height: 1.8;
}

/* ==================== */
/* Metrics */
/* ==================== */

.regression-metrics {
    margin: 3rem 0;
}

.regression-metrics h3 {
    color: var(--primary-color);
    margin-bottom: 2rem;
    font-size: 2rem;
}

.metric-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.metric-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.metric-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.metric-card h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.metric-range {
    margin-top: 1rem;
    padding: 0.8rem;
    background: var(--bg-alternate);
    border-radius: 8px;
    font-weight: 600;
    color: var(--primary-color);
}

.correlation-scale {
    display: flex;
    justify-content: space-between;
    margin-top: 1rem;
    padding: 1rem;
    background: linear-gradient(90deg, #ef4444, #fbbf24, #10b981);
    border-radius: 8px;
    color: white;
    font-size: 0.9rem;
    font-weight: 600;
}

/* ==================== */
/* Assumptions */
/* ==================== */

.assumptions-box {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow-md);
    margin: 2rem 0;
}

.assumptions-box h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.assumption-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.assumption-item {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    padding: 1rem;
    background: var(--bg-alternate);
    border-radius: 10px;
    transition: var(--transition);
}

.assumption-item:hover {
    background: #e0f2fe;
    transform: translateX(5px);
}

.check {
    color: var(--success-color);
    font-size: 1.5rem;
    font-weight: 700;
}

/* ==================== */
/* Calculator Section */
/* ==================== */

.calculator-tabs {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    justify-content: center;
}

.tab-button {
    padding: 1rem 2rem;
    background: white;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-color);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.tab-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.1), transparent);
    transition: left 0.5s;
}

.tab-button:hover::before {
    left: 100%;
}

.tab-button:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}

.tab-button.active {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border-color: var(--primary-color);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.calculator-content {
    display: none;
    background: white;
    padding: 2.5rem;
    border-radius: 20px;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.1);
    animation: fadeIn 0.5s ease;
    border: 1px solid var(--border-color);
}

.calculator-content.active {
    display: block;
}

.calculator-content h3 {
    color: var(--primary-color);
    margin-bottom: 2rem;
    font-size: 1.8rem;
}

.calculator-form {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group.full-width {
    grid-column: 1 / -1;
}

.form-group label {
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-color);
}

.form-group input,
.form-group select {
    padding: 0.8rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: var(--transition);
    font-family: 'Poppins', sans-serif;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.calculate-btn {
    grid-column: 1 / -1;
    padding: 1.2rem 2.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
    position: relative;
    overflow: hidden;
}

.calculate-btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.3);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.calculate-btn:hover::before {
    width: 300px;
    height: 300px;
}

.calculate-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(99, 102, 241, 0.4);
}

.calculate-btn:active {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.result-box {
    margin-top: 2rem;
    padding: 2rem;
    background: linear-gradient(135deg, #f8fafc, #e0f2fe);
    border-radius: 15px;
    border-left: 6px solid var(--primary-color);
    display: none;
    animation: fadeIn 0.5s ease;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.1);
}

.result-box.show {
    display: block;
}

.result-box h4 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    font-size: 1.6rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.result-box p {
    margin: 0.8rem 0;
    font-size: 1.05rem;
    line-height: 1.8;
    color: var(--text-color);
}

.result-box strong {
    color: var(--primary-dark);
    font-weight: 600;
}

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

/* ==================== */
/* Footer */
/* ==================== */

.footer {
    background: linear-gradient(135deg, #1e293b, #334155);
    color: white;
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
}

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

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

.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: var(--transition);
}

.footer-section a:hover {
    color: white;
    padding-left: 5px;
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.7);
}

/* ==================== */
/* Scroll to Top Button */
/* ==================== */

.scroll-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
    border-radius: 50%;
    font-size: 1.5rem;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    box-shadow: var(--shadow-lg);
    z-index: 999;
}

.scroll-top.show {
    opacity: 1;
    visibility: visible;
}

.scroll-top:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

/* ==================== */
/* Responsive Design */
/* ==================== */

/* Large Tablets and Small Desktops */
@media (max-width: 1200px) {
    .nav-container {
        padding: 0 20px;
    }

    .logo {
        font-size: 1.2rem;
    }

    .logo-icon {
        font-size: 1.6rem;
    }

    .nav-menu {
        gap: 0.3rem;
    }

    .nav-link {
        padding: 0.5rem 0.7rem;
        font-size: 0.85rem;
    }

    .hero-title {
        font-size: 3.2rem;
    }

    .content-grid,
    .test-grid,
    .level-grid {
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    }
}

@media (max-width: 1024px) {
    .nav-link {
        padding: 0.5rem 0.6rem;
        font-size: 0.8rem;
    }
}

/* Tablets */
@media (max-width: 900px) {
    .menu-toggle {
        display: flex;
        z-index: 1001;
    }

    .logo {
        font-size: 1.1rem;
        min-width: auto;
    }

    .logo-text {
        font-size: 1.1rem;
    }

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

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--primary-dark);
        flex-direction: column;
        gap: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.4s ease;
        box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
        flex-wrap: nowrap;
    }

    .nav-menu.active {
        max-height: 600px;
    }

    .nav-link {
        padding: 1.2rem;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
        text-align: center;
        font-size: 1rem;
        width: 100%;
    }

    .nav-link::before {
        display: none;
    }

    .hero {
        padding: 100px 20px 80px;
        min-height: 65vh;
    }

    .hero-title {
        font-size: 2.8rem;
    }

    .hero-subtitle {
        font-size: 1.2rem;
    }

    .cta-button {
        padding: 1rem 2.5rem;
        font-size: 1.1rem;
    }

    .section {
        padding: 60px 20px;
    }

    .section-title {
        font-size: 2.2rem;
    }

    .content-grid,
    .test-grid,
    .level-grid,
    .calculator-form {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .steps-container {
        grid-template-columns: 1fr;
    }

    .floating-stat {
        font-size: 2rem;
    }

    .correlation-scale {
        flex-direction: column;
        gap: 0.5rem;
        text-align: center;
    }

    .calculator-tabs {
        gap: 0.5rem;
    }

    .tab-button {
        padding: 0.8rem 1.5rem;
        font-size: 0.95rem;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

/* Mobile Devices */
@media (max-width: 480px) {
    .navbar {
        padding: 1rem 0;
    }

    .nav-container {
        padding: 0 15px;
    }

    .logo {
        font-size: 1rem;
        gap: 8px;
    }

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

    .logo-text {
        font-size: 1rem;
    }

    .hero {
        padding: 80px 15px 60px;
        min-height: 60vh;
    }

    .hero-title {
        font-size: 2rem;
        line-height: 1.3;
    }

    .hero-subtitle {
        font-size: 1rem;
        line-height: 1.6;
    }

    .cta-button {
        padding: 0.9rem 2rem;
        font-size: 1rem;
    }

    .section {
        padding: 50px 15px;
    }

    .section-title {
        font-size: 1.8rem;
    }

    .content-card,
    .test-card,
    .theory-box,
    .formula-box {
        padding: 1.5rem;
    }

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

    .calculator-tabs {
        flex-direction: column;
        gap: 0.5rem;
    }

    .tab-button {
        width: 100%;
        padding: 1rem;
    }

    .calculator-form {
        gap: 1rem;
    }

    .form-group input,
    .form-group select {
        font-size: 16px; /* Prevents zoom on iOS */
    }

    .floating-stat {
        font-size: 1.5rem;
    }

    .scroll-top {
        width: 45px;
        height: 45px;
        bottom: 20px;
        right: 20px;
        font-size: 1.3rem;
    }

    .error-grid,
    .anova-components,
    .regression-types,
    .metric-grid {
        grid-template-columns: 1fr;
    }

    .p-value-scale {
        grid-template-columns: 1fr;
    }
}

/* Extra Small Devices */
@media (max-width: 360px) {
    .logo {
        font-size: 0.95rem;
    }

    .logo-icon {
        font-size: 1.3rem;
    }

    .hero-title {
        font-size: 1.6rem;
    }

    .hero-subtitle {
        font-size: 0.9rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .content-card h3 {
        font-size: 1.2rem;
    }
}

/* Large Screens */
@media (min-width: 1400px) {
    .container {
        max-width: 1400px;
    }

    .nav-container {
        max-width: 1600px;
    }

    .logo {
        font-size: 1.5rem;
    }

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

    .nav-menu {
        gap: 0.8rem;
    }

    .nav-link {
        padding: 0.6rem 1.2rem;
        font-size: 0.95rem;
    }

    .hero-title {
        font-size: 4.5rem;
    }

    .hero-subtitle {
        font-size: 1.5rem;
    }

    .content-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

/* Ultra Wide Screens */
@media (min-width: 1920px) {
    .nav-container {
        max-width: 1800px;
    }

    .nav-link {
        padding: 0.6rem 1.5rem;
        font-size: 1rem;
    }
}

/* ==================== */
/* Print Styles */
/* ==================== */

@media print {
    .navbar,
    .hero-animation,
    .scroll-top,
    .menu-toggle,
    .calculator-content {
        display: none !important;
    }

    .section {
        page-break-inside: avoid;
    }
}