@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@300;400;500;600;700;800&display=swap');

:root {
    --primary-blue: #2563EB;
    --primary-glow: rgba(37, 99, 235, 0.18);
    --dark-blue: #1E3A8A;
    --dark-blue-glow: rgba(30, 58, 138, 0.15);
    --white: #FFFFFF;
    --black: #111111;
    --light-gray: #F8FAFC;
    --slate-100: #F1F5F9;
    --slate-200: #E2E8F0;
    --slate-300: #CBD5E1;
    --slate-600: #475569;
    --slate-700: #334155;
    --slate-800: #1E293B;
    --glass-bg: rgba(255, 255, 255, 0.75);
    --glass-border: rgba(226, 232, 240, 0.8);
    --font-main: 'Plus Jakarta Sans', sans-serif;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.02);
    --shadow-md: 0 8px 30px rgba(0,0,0,0.06);
    --shadow-lg: 0 20px 40px rgba(0,0,0,0.1);
    --shadow-glow: 0 0 25px rgba(37, 99, 235, 0.25);
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Base resets & Global Safety CSS */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html,
body {
    overflow-x: hidden;
    width: 100%;
}

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

body {
    font-family: var(--font-main);
    background-color: var(--light-gray);
    color: var(--slate-800);
    line-height: 1.6;
    position: relative;
}

img,
svg {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Background blobs */
body::before, body::after {
    content: '';
    position: absolute;
    width: 600px;
    height: 600px;
    border-radius: 50%;
    filter: blur(150px);
    z-index: -10;
    opacity: 0.4;
    pointer-events: none;
}

body::before {
    background: radial-gradient(circle, var(--primary-blue), transparent);
    top: -100px;
    right: -100px;
}

body::after {
    background: radial-gradient(circle, var(--dark-blue), transparent);
    bottom: 10%;
    left: -200px;
}

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

/* Layout containers */
.container {
    max-width: 1280px;
    width: 100%;
    margin: 0 auto;
    padding: 0 20px;
}

/* Button UI */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    font-size: 0.95rem;
    font-weight: 600;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    border: none;
    outline: none;
    gap: 0.5rem;
}

.btn-primary {
    background-color: var(--primary-blue);
    color: var(--white);
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
    background-color: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow);
}

.btn-secondary {
    background-color: var(--white);
    color: var(--slate-800);
    border: 1px solid var(--slate-200);
}

.btn-secondary:hover {
    background-color: var(--slate-100);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

/* Header */
header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 80px;
    background-color: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--glass-border);
    z-index: 1000;
    transition: var(--transition);
}

header.scrolled {
    height: 70px;
    background-color: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-sm);
}

header .container {
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    font-weight: 800;
    font-size: 1.4rem;
    color: var(--black);
    gap: 0.5rem;
}

.logo span {
    color: var(--primary-blue);
}

.logo svg {
    width: 32px;
    height: 32px;
    fill: var(--primary-blue);
}

/* Desktop Nav */
nav ul {
    display: flex;
    list-style: none;
    gap: 1.5rem;
    align-items: center;
}

nav ul li a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--slate-600);
    position: relative;
    padding: 0.5rem 0;
}

nav ul li a:hover {
    color: var(--primary-blue);
}

nav ul li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-blue);
    transition: var(--transition);
}

nav ul li a:hover::after {
    width: 100%;
}

.hamburger {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    z-index: 1001;
}

.hamburger span {
    display: block;
    width: 25px;
    height: 3px;
    background-color: var(--black);
    margin: 5px 0;
    transition: var(--transition);
}

/* Hero Section */
.hero {
    padding: 180px 0 100px;
    position: relative;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: 4rem;
    align-items: center;
}

.hero-left h1 {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.15;
    color: var(--black);
    margin-bottom: 1.5rem;
    letter-spacing: -0.02em;
}

.hero-left h1 span {
    background: linear-gradient(135deg, var(--primary-blue), var(--dark-blue));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-left p {
    font-size: 1.15rem;
    color: var(--slate-600);
    margin-bottom: 2.5rem;
    max-width: 550px;
}

.hero-btns {
    display: flex;
    gap: 1rem;
}

.hero-right {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 450px;
    max-width: 450px;
    width: 100%;
    margin: 0 auto;
}

.hero-animation-box {
    position: relative;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    max-width: 450px;
}

.floating-element {
    position: absolute;
    filter: drop-shadow(0 15px 25px rgba(37, 99, 235, 0.25));
    animation-iteration-count: infinite;
    animation-timing-function: ease-in-out;
}

.pi-symbol {
    font-size: 9rem;
    font-weight: 800;
    color: var(--primary-blue);
    opacity: 0.85;
    text-shadow: 0 0 30px var(--primary-glow);
    animation: floatPi 7s infinite ease-in-out, rotatePi 20s infinite linear;
}

.math-icon {
    top: 10%;
    left: 10%;
    width: 90px;
    height: 90px;
    background: linear-gradient(135deg, var(--primary-blue), var(--dark-blue));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 0 20px var(--primary-glow);
    animation: floatMath 8s infinite ease-in-out, rotateMath 15s infinite linear;
}

.math-icon svg {
    width: 45px;
    height: 45px;
    fill: var(--white);
}

.tech-icon {
    bottom: 15%;
    right: 10%;
    width: 100px;
    height: 100px;
    background: rgba(255,255,255,0.7);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(10px);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 0 25px rgba(37,99,235,0.15);
    animation: floatTech 6s infinite ease-in-out, rotateTech 25s infinite linear;
}

.tech-icon svg {
    width: 50px;
    height: 50px;
    fill: var(--primary-blue);
}

/* Animation Keyframes */
@keyframes floatPi {
    0%, 100% { transform: translateY(0px) scale(1); }
    50% { transform: translateY(-20px) scale(1.05); }
}

@keyframes rotatePi {
    0% { transform: translateY(0) rotate(0deg); }
    50% { transform: translateY(-10px) rotate(180deg); }
    100% { transform: translateY(0) rotate(360deg); }
}

@keyframes floatMath {
    0%, 100% { transform: translate(0px, 0px); }
    50% { transform: translate(15px, -25px); }
}

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

@keyframes floatTech {
    0%, 100% { transform: translate(0px, 0px); }
    50% { transform: translate(-20px, 20px); }
}

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

/* Category Filter Section */
.directory-section {
    padding: 60px 0 100px;
}

.section-header {
    text-align: center;
    margin-bottom: 3rem;
}

.section-header h2 {
    font-size: 2.25rem;
    color: var(--black);
    margin-bottom: 0.75rem;
}

.section-header p {
    color: var(--slate-600);
    max-width: 600px;
    margin: 0 auto;
}

.search-filter-wrapper {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(12px);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    margin-bottom: 3rem;
}

.search-box {
    position: relative;
    width: 100%;
    margin-bottom: 1.5rem;
}

.search-box input {
    width: 100%;
    padding: 1rem 1.5rem 1rem 3.5rem;
    font-size: 1.05rem;
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-sm);
    background-color: var(--white);
    font-family: var(--font-main);
    color: var(--black);
    outline: none;
    transition: var(--transition);
}

.search-box input:focus {
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 4px var(--primary-glow);
}

.search-box svg {
    position: absolute;
    left: 1.25rem;
    top: 50%;
    transform: translateY(-50%);
    width: 24px;
    height: 24px;
    fill: var(--slate-600);
}

/* Autocomplete List */
.autocomplete-suggestions {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--white);
    border: 1px solid var(--slate-200);
    border-top: none;
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
    z-index: 100;
    max-height: 250px;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
    display: none;
}

.autocomplete-suggestion {
    padding: 0.75rem 1.5rem;
    cursor: pointer;
    font-size: 0.95rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.autocomplete-suggestion:hover {
    background-color: var(--slate-100);
    color: var(--primary-blue);
}

.autocomplete-category {
    font-size: 0.75rem;
    background-color: var(--slate-200);
    color: var(--slate-600);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    text-transform: uppercase;
}

.filter-tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
}

.filter-tab {
    padding: 0.6rem 1.25rem;
    background: var(--white);
    border: 1px solid var(--slate-200);
    color: var(--slate-600);
    font-weight: 600;
    font-size: 0.9rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
}

.filter-tab:hover, .filter-tab.active {
    background-color: var(--primary-blue);
    color: var(--white);
    border-color: var(--primary-blue);
    box-shadow: 0 4px 12px var(--primary-glow);
}

/* Cards Grid */
.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(290px, 1fr));
    gap: 2rem;
}

.calc-card {
    background: var(--white);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 2rem;
    display: flex;
    flex-direction: column;
    height: 100%;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.calc-card::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-blue), var(--dark-blue));
    opacity: 0;
    transition: var(--transition);
}

.calc-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    border-color: rgba(37,99,235,0.25);
}

.calc-card:hover::after {
    opacity: 1;
}

.card-icon {
    width: 54px;
    height: 54px;
    background-color: var(--slate-100);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.5rem;
    color: var(--primary-blue);
    transition: var(--transition);
}

.calc-card:hover .card-icon {
    background-color: var(--primary-blue);
    color: var(--white);
}

.card-icon svg {
    width: 28px;
    height: 28px;
    fill: currentColor;
}

.calc-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--black);
    margin-bottom: 0.75rem;
}

.calc-card p {
    color: var(--slate-600);
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.card-link {
    display: inline-flex;
    align-items: center;
    color: var(--primary-blue);
    font-weight: 600;
    font-size: 0.9rem;
    gap: 0.5rem;
}

.card-link svg {
    width: 16px;
    height: 16px;
    fill: currentColor;
    transition: var(--transition);
}

.calc-card:hover .card-link svg {
    transform: translateX(4px);
}

/* Calculator Detail Page */
.page-header {
    padding: 140px 0 40px;
    background-color: var(--white);
    border-bottom: 1px solid var(--slate-200);
}

.breadcrumbs {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    color: var(--slate-600);
    margin-bottom: 1.5rem;
}

.breadcrumbs a:hover {
    color: var(--primary-blue);
}

.breadcrumbs span {
    color: var(--slate-300);
}

.page-header h1 {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--black);
    line-height: 1.2;
}

.calculator-wrapper {
    padding: 60px 0 100px;
}

.calculator-layout {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 3.5rem;
    align-items: start;
}

/* Calculator Sandbox */
.calculator-sandbox {
    background: var(--white);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 2.5rem;
    box-shadow: var(--shadow-md);
    margin-bottom: 3rem;
}

.calculator-sandbox h2 {
    font-size: 1.5rem;
    margin-bottom: 2rem;
    color: var(--black);
    border-bottom: 2px solid var(--slate-100);
    padding-bottom: 0.75rem;
}

.calculator-inputs {
    display: grid;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.input-group label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--slate-700);
}

.input-group input, .input-group select, .input-group textarea {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-sm);
    font-family: var(--font-main);
    font-size: 1rem;
    outline: none;
    transition: var(--transition);
}

.input-group input:focus, .input-group select:focus, .input-group textarea:focus {
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px var(--primary-glow);
}

.input-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.calculator-outputs {
    background-color: var(--light-gray);
    border-radius: var(--radius-sm);
    padding: 1.5rem;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
    margin-top: 2rem;
    border: 1px solid var(--slate-200);
}

.output-card {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.output-card span {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--slate-600);
    text-transform: uppercase;
}

.output-card h3 {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--primary-blue);
}

.output-card.full-width {
    grid-column: span 2;
    border-top: 1px solid var(--slate-200);
    padding-top: 1rem;
}

/* Rich text content section */
.calculator-article {
    background-color: var(--white);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 3rem;
    box-shadow: var(--shadow-md);
}

.calculator-article section {
    margin-bottom: 2.5rem;
}

.calculator-article section:last-child {
    margin-bottom: 0;
}

.calculator-article h2 {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--black);
    margin-bottom: 1.25rem;
}

.calculator-article h3 {
    font-size: 1.35rem;
    font-weight: 600;
    color: var(--slate-800);
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
}

.calculator-article p {
    font-size: 1rem;
    color: var(--slate-600);
    margin-bottom: 1.25rem;
}

.calculator-article ul, .calculator-article ol {
    margin-left: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--slate-600);
}

.calculator-article li {
    margin-bottom: 0.5rem;
}

.formula-block {
    background-color: var(--slate-100);
    border-left: 4px solid var(--primary-blue);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    padding: 1.5rem;
    margin: 1.5rem 0;
    font-size: 1.1rem;
    text-align: center;
    font-family: 'Courier New', Courier, monospace;
    font-weight: bold;
    color: var(--slate-800);
    overflow-x: auto;
}

/* Sidebar elements */
.sidebar-box {
    background-color: var(--white);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-sm);
}

.sidebar-box h3 {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--black);
    margin-bottom: 1.25rem;
    border-bottom: 2px solid var(--slate-100);
    padding-bottom: 0.5rem;
}

.related-list {
    list-style: none;
}

.related-list li {
    margin-bottom: 0.75rem;
}

.related-list li a {
    display: flex;
    align-items: center;
    font-size: 0.95rem;
    color: var(--slate-700);
    gap: 0.5rem;
}

.related-list li a:hover {
    color: var(--primary-blue);
    transform: translateX(3px);
}

.related-list li a svg {
    width: 14px;
    height: 14px;
    fill: currentColor;
}

/* FAQ Accordions */
.faq-accordion {
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-bottom: 1rem;
}

.faq-header {
    background-color: var(--slate-100);
    padding: 1rem 1.5rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-header:hover {
    background-color: var(--slate-200);
}

.faq-header .icon {
    font-size: 1.2rem;
    font-weight: bold;
    transition: var(--transition);
}

.faq-accordion.active .faq-header .icon {
    transform: rotate(45deg);
}

.faq-content {
    padding: 1.25rem 1.5rem;
    background-color: var(--white);
    display: none;
    border-top: 1px solid var(--slate-200);
}

/* Call to Action (CTA) */
.cta-box {
    background: linear-gradient(135deg, var(--primary-blue), var(--dark-blue));
    color: var(--white);
    padding: 3.5rem 2rem;
    border-radius: var(--radius-md);
    text-align: center;
    margin-top: 4rem;
    box-shadow: var(--shadow-lg);
}

.cta-box h2 {
    font-size: 2.25rem;
    font-weight: 800;
    margin-bottom: 1rem;
}

.cta-box p {
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto 2rem;
    opacity: 0.9;
}

/* Static page adjustments */
.static-page-wrapper {
    padding: 140px 0 100px;
}

.static-page-layout {
    max-width: 900px;
    margin: 0 auto;
    background-color: var(--white);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 4rem;
    box-shadow: var(--shadow-md);
}

.static-page-layout h1 {
    font-size: 2.75rem;
    font-weight: 800;
    margin-bottom: 1rem;
}

.static-page-layout .updated-date {
    font-size: 0.9rem;
    color: var(--slate-600);
    margin-bottom: 3rem;
    border-bottom: 1px solid var(--slate-200);
    padding-bottom: 1rem;
}

.static-page-layout h2 {
    font-size: 1.75rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
}

.static-page-layout p {
    font-size: 1.05rem;
    margin-bottom: 1.5rem;
}

.static-page-layout ul {
    margin-left: 2rem;
    margin-bottom: 1.5rem;
}

/* Contact Form Specifics */
.contact-form-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    margin-top: 3rem;
}

.contact-info h3 {
    font-size: 1.4rem;
    margin-bottom: 1.5rem;
}

.contact-info-item {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.contact-info-item svg {
    width: 24px;
    height: 24px;
    fill: var(--primary-blue);
    flex-shrink: 0;
}

.contact-form-wrapper {
    background-color: var(--light-gray);
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    padding: 2.5rem;
}

/* Footer styling */
footer {
    background-color: var(--slate-800);
    color: var(--slate-300);
    padding: 80px 0 40px;
    border-top: 1px solid var(--slate-700);
    position: relative;
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.2fr 0.9fr 0.9fr 1fr;
    gap: 4rem;
    margin-bottom: 4rem;
}

.footer-col h4 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--white);
    margin-bottom: 1.5rem;
    position: relative;
}

.footer-col h4::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 30px;
    height: 2px;
    background-color: var(--primary-blue);
}

.footer-col p {
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
}

.footer-socials {
    display: flex;
    gap: 1rem;
}

.social-icon {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    background-color: var(--slate-700);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    transition: var(--transition);
}

.social-icon svg {
    width: 18px;
    height: 18px;
    fill: currentColor;
}

.social-icon.fb:hover { background-color: #1877F2; }
.social-icon.ig:hover { background-color: #E4405F; }
.social-icon.tw:hover { background-color: #000000; }
.social-icon.li:hover { background-color: #0A66C2; }

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.75rem;
}

.footer-links li a:hover {
    color: var(--white);
    padding-left: 4px;
}

.footer-bottom {
    border-top: 1px solid var(--slate-700);
    padding-top: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
    font-size: 0.9rem;
}

/* Back To Top Button */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background-color: var(--primary-blue);
    color: var(--white);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow-glow);
    z-index: 99;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    border: none;
    outline: none;
}

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

.back-to-top:hover {
    transform: translateY(-5px);
    background-color: #1d4ed8;
}

.back-to-top svg {
    width: 20px;
    height: 20px;
    fill: currentColor;
}


/* ==========================================
   Calculator.net Structure Upgrade & Repairs
   ========================================== */

/* 1. Desktop Dropdowns */
.dropdown {
    position: relative;
}

.dropdown-toggle {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.dropdown-toggle .arrow {
    font-size: 0.65rem;
    transition: transform 0.3s ease;
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%) translateY(15px);
    width: 260px;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-md);
    opacity: 0;
    visibility: hidden;
    padding: 0.75rem 0;
    display: flex;
    flex-direction: column;
    z-index: 1050;
    transition: opacity 0.3s ease, transform 0.3s ease, visibility 0.3s ease;
}

.dropdown-menu::before {
    content: '';
    position: absolute;
    bottom: 100%;
    left: 50%;
    transform: translateX(-50%);
    border-width: 6px;
    border-style: solid;
    border-color: transparent transparent rgba(255, 255, 255, 0.95) transparent;
}

.dropdown-menu li {
    width: 100%;
}

.dropdown-menu li a {
    display: block;
    padding: 0.6rem 1.25rem;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--slate-700);
    transition: var(--transition);
    border-bottom: none;
    position: relative;
}

.dropdown-menu li a::after {
    display: none !important;
}

.dropdown-menu li a:hover {
    color: var(--primary-blue);
    background-color: var(--slate-100);
    padding-left: 1.5rem;
}

.dropdown-menu li a.view-all {
    border-top: 1px solid var(--slate-200);
    margin-top: 0.5rem;
    padding-top: 0.75rem;
    color: var(--primary-blue);
    font-weight: 600;
}

.dropdown-menu li a.view-all:hover {
    background: transparent;
    padding-left: 1.25rem;
    color: var(--dark-blue);
}

@media (min-width: 769px) {
    .dropdown:hover .dropdown-menu,
    .dropdown.active .dropdown-menu {
        opacity: 1;
        visibility: visible;
        transform: translateX(-50%) translateY(5px);
    }
}

/* 2. Mobile Nav & Collapsible Menu overlays */
.menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.45);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    z-index: 999;
}

.menu-overlay.active {
    opacity: 1;
    visibility: visible;
}

.menu-close {
    display: none;
}

/* 3. Homepage Category Blocks */
.category-block {
    margin-top: 4rem;
    padding-top: 1rem;
}

.category-block-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 2px solid var(--slate-200);
    padding-bottom: 0.75rem;
    margin-bottom: 2rem;
}

.category-block-header h2 {
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--black);
    position: relative;
}

.category-block-header h2::after {
    content: '';
    position: absolute;
    bottom: -11px;
    left: 0;
    width: 60px;
    height: 3px;
    background-color: var(--primary-blue);
}

.view-category-btn {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--primary-blue);
    transition: var(--transition);
}

.view-category-btn:hover {
    color: var(--dark-blue);
    transform: translateX(4px);
}

/* 4. Previous / Next Calculator Pagination */
.calculator-nav-prev-next {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--slate-200);
    padding-bottom: 1rem;
    font-size: 0.85rem;
    font-weight: 600;
}

.prev-calc-btn, .next-calc-btn {
    color: var(--slate-600);
    transition: var(--transition);
    padding: 0.4rem 0.8rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--slate-200);
    background: var(--white);
}

.prev-calc-btn:hover, .next-calc-btn:hover {
    color: var(--primary-blue);
    border-color: var(--primary-blue);
    background: var(--slate-100);
}

.prev-calc-btn:hover {
    transform: translateX(-3px);
}

.next-calc-btn:hover {
    transform: translateX(3px);
}

/* ==========================================
   Media Queries & Responsiveness
   ========================================== */

/* 1024px to 1439px (Laptop) */
@media (max-width: 1024px) {
    .hero-grid {
        gap: 2rem;
    }
    .hero-left h1 {
        font-size: 2.8rem;
    }
    .hero-right {
        height: 380px;
    }
    .pi-symbol {
        font-size: 7.5rem;
    }
    .math-icon {
        width: 75px;
        height: 75px;
    }
    .tech-icon {
        width: 80px;
        height: 80px;
    }
    .calculator-layout {
        grid-template-columns: 1.1fr 0.9fr;
        gap: 2rem;
    }
    .footer-grid {
        gap: 2rem;
    }
}

/* 768px to 1023px (Tablet) */
@media (max-width: 768px) {
    header {
        height: 70px;
    }
    .hamburger {
        display: block;
    }
    .hamburger.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    .hamburger.active span:nth-child(2) {
        opacity: 0;
    }
    .hamburger.active span:nth-child(3) {
        transform: rotate(-45deg) translate(7px, -8px);
    }
    nav {
        position: fixed;
        top: 0;
        left: -320px;
        width: 320px;
        max-width: 100%;
        height: 100vh;
        background-color: var(--white);
        padding: 5rem 2rem 3rem;
        transition: var(--transition);
        box-shadow: var(--shadow-lg);
        overflow-y: auto;
        z-index: 1000;
    }
    nav.active {
        left: 0;
    }
    nav ul {
        flex-direction: column;
        align-items: flex-start;
        gap: 1.5rem;
    }
    nav ul li a {
        font-size: 1.1rem;
        width: 100%;
    }
    .menu-close {
        display: block;
        position: absolute;
        top: 20px;
        right: 20px;
        font-size: 2rem;
        background: none;
        border: none;
        cursor: pointer;
        color: var(--black);
        z-index: 1002;
    }
    /* Mobile Dropdown Collapsible */
    .dropdown-menu {
        position: static;
        width: 100%;
        opacity: 1;
        visibility: visible;
        transform: none;
        box-shadow: none;
        border: none;
        background: transparent;
        padding-left: 1rem;
        display: none;
        transition: none;
    }
    .dropdown-menu::before {
        display: none;
    }
    .dropdown.active .dropdown-menu {
        display: flex;
    }
    .dropdown-toggle {
        justify-content: space-between;
        width: 100%;
    }
    .dropdown.active .dropdown-toggle .arrow {
        transform: rotate(180deg);
    }
    .hero {
        padding: 120px 0 60px;
    }
    .hero-grid {
        grid-template-columns: 1fr;
        gap: 3rem;
        text-align: center;
    }
    .hero-left p {
        margin: 0 auto 2rem;
    }
    .hero-btns {
        justify-content: center;
    }
    .hero-right {
        height: 300px;
    }
    .calculator-layout {
        grid-template-columns: 1fr;
    }
    .contact-form-grid {
        grid-template-columns: 1fr;
        gap: 2.5rem;
    }
    .footer-grid {
        grid-template-columns: 1fr 1fr;
        gap: 2.5rem;
    }
    .static-page-layout {
        padding: 2.5rem;
    }
}

/* 425px to 767px (Large Mobile) */
@media (max-width: 425px) {
    html {
        font-size: 15px;
    }
    .container {
        padding: 0 1.25rem;
    }
    .hero-left h1 {
        font-size: 2.2rem;
    }
    .hero-btns {
        flex-direction: column;
        width: 100%;
    }
    .hero-btns .btn {
        width: 100%;
    }
    .pi-symbol {
        font-size: 6rem;
    }
    .filter-tabs {
        gap: 0.5rem;
    }
    .filter-tab {
        padding: 0.5rem 1rem;
        font-size: 0.85rem;
    }
    .cards-grid {
        grid-template-columns: 1fr;
    }
    .calculator-sandbox {
        padding: 1.5rem;
    }
    .calculator-outputs {
        grid-template-columns: 1fr;
    }
    .output-card.full-width {
        grid-column: span 1;
    }
    .calculator-article {
        padding: 1.5rem;
    }
    .static-page-layout {
        padding: 1.5rem;
    }
    .footer-grid {
        grid-template-columns: 1fr;
    }
    .footer-bottom {
        flex-direction: column;
        text-align: center;
    }
}

/* 320px to 424px (Small Mobile) */
@media (max-width: 320px) {
    .hero-left h1 {
        font-size: 1.85rem;
    }
    .logo {
        font-size: 1.2rem;
    }
}

/* ==========================================
   Tool-Specific Custom Upgrades (BMI, Mortgage, Amortization, Scientific)
   ========================================== */

/* Unit Toggle buttons */
.unit-toggle-row {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.unit-toggle-row .btn.active {
    background-color: var(--primary-blue);
    color: var(--white);
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

/* BMI badge classifications */
.bmi-badge {
    display: inline-block;
    padding: 0.35rem 0.8rem;
    font-size: 0.9rem;
    font-weight: 700;
    border-radius: var(--radius-sm);
    color: var(--white);
    margin-top: 0.5rem;
    text-align: center;
}
.bmi-underweight { background-color: #f59e0b; }
.bmi-normal { background-color: #10b981; }
.bmi-overweight { background-color: #f97316; }
.bmi-obese { background-color: #ef4444; }

/* Amortization Table styling */
.amortization-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1.5rem;
    font-size: 0.95rem;
}
.amortization-table th, .amortization-table td {
    padding: 0.75rem 1rem;
    text-align: right;
    border-bottom: 1px solid var(--slate-200);
}
.amortization-table th:first-child, .amortization-table td:first-child {
    text-align: left;
}
.amortization-table th {
    background-color: var(--slate-100);
    font-weight: 700;
    color: var(--slate-800);
}
.amortization-table tr:hover {
    background-color: rgba(37, 99, 235, 0.03);
}

/* Mortgage breakdown conic-gradient chart */
.mortgage-breakdown-chart-wrapper {
    margin-top: 1rem;
    display: flex;
    flex-direction: column;
    align-items: center;
}
.mortgage-chart {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    margin: 1.5rem 0;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}
.chart-legend {
    list-style: none;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    font-size: 0.9rem;
}
.chart-legend li {
    display: flex;
    align-items: center;
    justify-content: space-between;
}
.legend-color {
    display: inline-block;
    width: 12px;
    height: 12px;
    border-radius: 3px;
    margin-right: 8px;
}
.legend-color.p-and-i { background-color: var(--primary-blue); }
.legend-color.taxes { background-color: #f43f5e; }
.legend-color.insurance { background-color: #10b981; }
.legend-color.hoa { background-color: #eab308; }

/* Scientific Calculator Layout styling */
.scientific-calc {
    max-width: 500px;
    margin: 0 auto;
}
.calc-display-wrapper {
    background: var(--slate-800);
    border-radius: var(--radius-sm);
    padding: 1rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow-sm);
}
.calc-mode-indicator {
    display: flex;
    justify-content: flex-start;
    font-size: 0.75rem;
    color: var(--slate-300);
    margin-bottom: 0.25rem;
}
#calc_screen {
    width: 100%;
    border: none;
    background: transparent;
    color: var(--white);
    font-family: monospace;
    font-size: 1.8rem;
    text-align: right;
    outline: none;
}
.scientific-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 0.5rem;
}
.scientific-grid .btn {
    padding: 0.65rem 0.25rem;
    font-size: 0.85rem;
    font-weight: 700;
    border-radius: var(--radius-sm);
}
.scientific-grid .num-btn {
    background-color: var(--white);
    color: var(--slate-800);
    border: 1px solid var(--slate-200);
}
.scientific-grid .num-btn:hover {
    background-color: var(--slate-100);
}
.scientific-grid .mode-btn {
    background-color: var(--slate-700);
    color: var(--white);
}
.scientific-grid .mode-btn:hover {
    background-color: var(--slate-800);
}

/* Age date selectors layout */
.date-selects {
    display: flex;
    gap: 0.5rem;
}
.date-selects select, .date-selects input {
    flex: 1;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--slate-200);
    outline: none;
}
.main-age-result, .countdown-card {
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.05), rgba(30, 58, 138, 0.05));
    border: 1px solid rgba(37, 99, 235, 0.15);
}
.main-age-result h3 {
    color: var(--primary-blue);
    font-size: 1.8rem;
    font-weight: 800;
    margin-top: 0.5rem;
}
.countdown-card h3 {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--slate-700);
    margin-top: 0.5rem;
}
.results-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-top: 1rem;
    margin-bottom: 1rem;
}
@media (max-width: 425px) {
    .results-grid {
        grid-template-columns: 1fr;
    }
}