:root {
    --primary: #1e3a8a;
    --bg: #ffffff;
    --bg-light: #f8fafc;
    --accent: #e2e8f0;
    --text: #1f2937;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
}

.navbar {
    background: var(--primary) !important;
    box-shadow: 0 8px 24px var(--accent);
}

.navbar-brand,
.navbar .nav-link,
.navbar .navbar-toggler {
    color: var(--bg) !important;
}

.navbar .nav-link {
    font-weight: 500;
}

.hero-section {
    background: var(--bg-light);
    padding: 2.5rem 0 1.5rem;
}

.hero-section h1 {
    color: var(--primary);
    font-size: clamp(1.8rem, 4.2vw, 2.6rem);
    line-height: 1.2;
    margin-bottom: 0.9rem;
}

.hero-section p {
    margin: 0 auto;
    max-width: 900px;
}

.calculator-card {
    margin: 0 auto;
    margin-top: -0.5rem;
    margin-bottom: 2rem;
    max-width: 700px;
    width: 100%;
    background: var(--bg);
    border: 1px solid var(--accent);
    border-radius: 14px;
    box-shadow: 0 12px 28px var(--accent);
    padding: 1rem;
}

.calculator-card h3 {
    color: var(--primary);
    text-align: center;
    margin-bottom: 1rem;
}

.form-group-row {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.85rem;
    margin-bottom: 0.85rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.45rem;
    font-weight: 600;
}

.form-control,
.form-select {
    width: 100%;
    border: 1px solid var(--accent);
    border-radius: 10px;
    background: var(--bg);
    color: var(--text);
    min-height: 52px;
    font-size: 1rem;
}

.form-control:focus,
.form-select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px var(--accent);
}

.calculator-buttons {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.6rem;
    margin: 0.7rem 0;
}

.btn-calculate,
.btn-reset,
.btn-example {
    width: 100%;
    min-height: 50px;
    border-radius: 10px;
    border: 1px solid var(--primary);
    font-size: 1rem;
    font-weight: 600;
    padding: 0.65rem 1rem;
}

.btn-calculate {
    background: var(--primary);
    color: var(--bg);
}

.btn-reset,
.btn-example {
    background: var(--bg-light);
    color: var(--text);
    border-color: var(--accent);
}

.results-card {
    margin-top: 1rem;
    border: 1px solid var(--accent);
    border-left: 5px solid var(--primary);
    border-radius: 10px;
    background: var(--bg-light);
    padding: 1rem;
    display: none;
}

.results-card.show {
    display: block;
}

.results-title {
    text-align: center;
    margin-bottom: 0.8rem;
    color: var(--primary);
    font-weight: 700;
}

.result-item {
    padding: 0.7rem 0;
    border-bottom: 1px solid var(--accent);
}

.result-item:last-child {
    border-bottom: 0;
}

.result-label {
    font-size: 0.95rem;
}

.result-value {
    color: var(--primary);
    font-size: 1.2rem;
    font-weight: 700;
}

main {
    padding: 1rem 0 2.2rem;
}

section {
    padding: 1.4rem 0;
    border-bottom: 1px solid var(--accent);
}

section:last-of-type {
    border-bottom: 0;
}

h2 {
    color: var(--primary);
    font-size: clamp(1.25rem, 3.4vw, 1.9rem);
    margin-bottom: 0.75rem;
}

h3 {
    color: var(--text);
    font-size: 1.1rem;
    margin-top: 1rem;
    margin-bottom: 0.45rem;
}

p,
li {
    color: var(--text);
}

ul,
ol {
    padding-left: 1.2rem;
}

.formula-box,
.example-box {
    background: var(--bg-light);
    border: 1px solid var(--accent);
    border-radius: 10px;
    padding: 1rem;
}

.formula-variable {
    color: var(--primary);
    font-weight: 700;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--bg);
    border: 1px solid var(--accent);
}

th,
td {
    border: 1px solid var(--accent);
    padding: 0.65rem;
    text-align: left;
}

th {
    background: var(--bg-light);
    color: var(--primary);
}

.faq-item {
    border: 1px solid var(--accent);
    border-radius: 10px;
    background: var(--bg);
    margin-bottom: 0.7rem;
    overflow: hidden;
}

.faq-question {
    padding: 0.9rem;
    background: var(--bg-light);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.75rem;
    font-weight: 600;
}

.faq-question.active {
    background: var(--accent);
}

.faq-answer {
    display: none;
    padding: 0.9rem;
}

.faq-answer.show {
    display: block;
}

.calculator-links {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.6rem;
}

.calc-link {
    display: block;
    text-decoration: none;
    color: var(--primary);
    background: var(--bg-light);
    border: 1px solid var(--accent);
    border-radius: 10px;
    padding: 0.8rem;
    font-weight: 600;
}

footer,
footer.bg-dark {
    background: var(--primary) !important;
    color: var(--bg) !important;
    border-top: 1px solid var(--accent);
}

footer h5,
footer p,
footer a,
footer li,
footer .text-muted,
footer .text-white {
    color: var(--bg) !important;
}

footer hr {
    border-color: var(--accent) !important;
    opacity: 1;
}

@media (min-width: 768px) {
    .hero-section {
        padding: 3rem 0 2rem;
    }

    .calculator-card {
        padding: 1.5rem;
    }

    .form-group-row {
        grid-template-columns: 1fr 1fr;
    }

    .calculator-buttons {
        grid-template-columns: 1fr 1fr;
    }

    .btn-calculate {
        margin-top: 0.2rem;
    }

    .calculator-links {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

/* Content Pages Styling */
.content-section {
    margin-bottom: 2.5rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--accent);
}

.content-section:last-child {
    border-bottom: 0;
}

.content-section h2 {
    margin-top: 0;
    margin-bottom: 1rem;
}

.content-section h3 {
    margin-top: 1.2rem;
    margin-bottom: 0.6rem;
    font-weight: 600;
}

.content-section h4 {
    color: var(--primary);
    font-size: 1rem;
    margin-top: 0.8rem;
    margin-bottom: 0.4rem;
    font-weight: 600;
}

.content-section ul {
    margin-left: 0.5rem;
}

.content-section li {
    margin-bottom: 0.5rem;
    line-height: 1.8;
}

.formula-box {
    background: var(--bg-light);
    border-left: 4px solid var(--primary);
    border-radius: 8px;
    padding: 1.2rem;
    margin: 1.5rem 0;
    text-align: center;
}

.formula-box p {
    margin: 0;
    font-size: 1.1rem;
    color: var(--primary);
}

/* Contact Form Styling */
.contact-section,
.contact-info,
.faq-section {
    background: var(--bg);
}

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

.contact-form .form-control {
    border: 1px solid var(--accent);
    border-radius: 8px;
    padding: 0.7rem;
    font-size: 0.95rem;
}

.contact-form .form-control:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(30, 58, 138, 0.1);
}

.contact-info h4 {
    color: var(--primary);
    margin-bottom: 0.8rem;
}

.contact-info p {
    margin-bottom: 0.6rem;
    line-height: 1.8;
}

.contact-info a {
    color: var(--primary);
    text-decoration: none;
    font-weight: 500;
}

.contact-info a:hover {
    text-decoration: underline;
}

/* Accordion Styling */
.accordion-button {
    color: var(--text);
    background-color: var(--bg-light);
    border-color: var(--accent);
    font-weight: 500;
}

.accordion-button:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 0.25rem rgba(30, 58, 138, 0.15);
}

.accordion-button:not(.collapsed) {
    color: var(--bg);
    background-color: var(--primary);
    box-shadow: inset 0 -1px 0 rgba(0, 0, 0, 0.125);
}

.accordion-body {
    padding: 1.2rem;
    background: var(--bg);
    border-top: 1px solid var(--accent);
    line-height: 1.8;
}

/* Button Styling */
.btn-primary {
    background-color: var(--primary);
    border-color: var(--primary);
    font-weight: 600;
    transition: all 0.3s ease;
}

.btn-primary:hover,
.btn-primary:focus {
    background-color: #1a2f6b;
    border-color: #1a2f6b;
    box-shadow: 0 4px 12px rgba(30, 58, 138, 0.3);
}

.btn-lg {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
}

/* Alert Styling */
.alert {
    border-radius: 8px;
    border: 1px solid;
}

.alert-success {
    background-color: #d1fae5;
    border-color: #6ee7b7;
    color: #065f46;
}

.alert-danger {
    background-color: #fee2e2;
    border-color: #fca5a5;
    color: #7f1d1d;
}

/* Footer Enhancements */
footer a {
    transition: opacity 0.3s ease;
}

footer a:hover {
    opacity: 0.8;
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
}

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

/* Smooth panel reveal */
.fade-panel {
    opacity: 0;
    transition: opacity 0.2s ease;
}

.fade-panel.is-visible {
    opacity: 1;
}

/* Copy Link micro-interaction */
.copy-link-btn {
    transition: transform 0.25s ease, background-color 0.25s ease, border-color 0.25s ease, color 0.25s ease;
    transform: scale(1);
}

.copy-link-btn.is-copied {
    transform: scale(1.05);
    background-color: #065f46 !important;
    border-color: #065f46 !important;
    color: #ffffff !important;
}

.copy-link-btn .copy-tick {
    color: #6ee7b7;
    font-weight: 800;
    display: inline-block;
    margin-left: 0.25rem;
}

/* Calculator alerts spacing */
.calculator-card #calcError,
.calculator-card #calcNotice {
    margin-top: 1rem;
    margin-bottom: 1rem;
}

.share-url {
    font-size: 0.95rem;
    word-break: break-all;
}