/* CSS Variables for Consistent Color Scheme */
:root {
    --bg-color: #ffffff;
    --text-color: #333333;
    --text-color-dark: #000000;
    --accent-color: #0056b3;
    --border-color: #333333;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "San Francisco", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header and Navigation */
header {
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
}

nav a {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
}

nav a:hover {
    color: var(--accent-color);
}

/* Main Content */
main {
    flex: 1;
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1rem;
    width: 100%;
}

/* Tool Heading Section */
#home {
    text-align: center;
    margin-bottom: 3rem;
}

h1 {
    font-size: 2.5rem;
    color: var(--text-color-dark);
    margin-bottom: 1rem;
}

.subheading {
    font-size: 1.2rem;
    color: var(--text-color);
}

/* Measurement Guide Section */
.measurement-guide {
    margin-bottom: 3rem;
}

.measurement-guide h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

.measurement-item {
    margin-bottom: 2.5rem;
    border: 1px solid var(--border-color);
    padding: 1.5rem;
}

.measurement-item h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-color-dark);
}

.measurement-image {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 1rem 0;
    border: 1px solid var(--border-color);
}

.measurement-item p {
    margin-bottom: 0.5rem;
}

/* Calculator Section */
.calculator-section {
    margin-bottom: 3rem;
    border: 1px solid var(--border-color);
    padding: 2rem;
}

.calculator-section h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

#faceShapeForm {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Unit Toggle Styles */
.unit-toggle-group {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    border: 1px solid var(--border-color);
    background-color: var(--bg-color);
}

.unit-toggle-label {
    font-weight: 500;
    color: var(--text-color-dark);
    margin: 0;
}

.unit-toggle {
    display: flex;
    gap: 0;
    border: 1px solid var(--border-color);
}

.unit-toggle input[type="radio"] {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
}

.unit-toggle .unit-option {
    padding: 0.75rem 1.5rem;
    border: none;
    background-color: var(--bg-color);
    color: var(--text-color);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    font-family: inherit;
    border-right: 1px solid var(--border-color);
    margin: 0;
}

.unit-toggle .unit-option:last-of-type {
    border-right: none;
}

.unit-toggle input[type="radio"]:checked + .unit-option {
    background-color: var(--accent-color);
    color: var(--bg-color);
}

.unit-toggle .unit-option:hover {
    background-color: #e6f0ff;
}

.unit-toggle input[type="radio"]:checked + .unit-option:hover {
    background-color: #004494;
}

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

.input-group label {
    font-weight: 500;
    color: var(--text-color-dark);
}

.input-group input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    font-size: 1rem;
    font-family: inherit;
    color: var(--text-color-dark);
    background-color: var(--bg-color);
}

.input-group input:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

#calculateBtn {
    padding: 1rem 2rem;
    background-color: var(--accent-color);
    color: var(--bg-color);
    border: 1px solid var(--accent-color);
    font-size: 1.1rem;
    font-weight: 500;
    cursor: pointer;
    font-family: inherit;
}

#calculateBtn:hover {
    background-color: #004494;
    border-color: #004494;
}

#calculateBtn:active {
    background-color: #003d82;
}

/* Result Display */
.result-container {
    margin-top: 2rem;
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    display: none;
}

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

.result-container h3 {
    font-size: 1.8rem;
    margin-bottom: 1rem;
    color: var(--text-color-dark);
}

.result-container p {
    font-size: 1.1rem;
    line-height: 1.8;
}

/* Related Tools Section */
.related-tools {
    margin-bottom: 3rem;
}

.related-tools h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

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

.tool-link {
    padding: 1rem;
    border: 1px solid var(--border-color);
    text-align: center;
    text-decoration: none;
    color: var(--text-color);
    display: block;
}

.tool-link:hover {
    background-color: var(--accent-color);
    color: var(--bg-color);
    border-color: var(--accent-color);
}

/* SEO Content Section */
.seo-content {
    margin-bottom: 3rem;
}

.seo-content h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

.seo-content p {
    margin-bottom: 1rem;
    font-size: 1rem;
    line-height: 1.7;
}

/* How-to-Use Section */
.how-to-use {
    margin-bottom: 3rem;
}

.how-to-use h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

.how-to-use ol {
    margin-left: 2rem;
    line-height: 2;
}

.how-to-use li {
    margin-bottom: 0.5rem;
}

/* FAQs Section */
.faqs {
    margin-bottom: 3rem;
}

.faqs h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

.faq-item {
    margin-bottom: 1.5rem;
    border: 1px solid var(--border-color);
    padding: 1.5rem;
}

.faq-question {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: var(--text-color-dark);
}

.faq-answer {
    font-size: 1rem;
    line-height: 1.7;
}

/* References Section */
.references {
    margin-bottom: 3rem;
}

.references h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-color-dark);
}

.references p {
    font-size: 1rem;
    line-height: 1.7;
}

/* Footer */
footer {
    border-top: 1px solid var(--border-color);
    padding: 2rem 1rem;
    text-align: center;
    margin-top: auto;
}

footer p {
    margin-bottom: 1rem;
    color: var(--text-color);
}

footer nav {
    margin-top: 1rem;
}

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

footer a:hover {
    color: var(--accent-color);
}

/* Responsive Design - Mobile First */
@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }

    .subheading {
        font-size: 1rem;
    }

    main {
        padding: 1rem 0.5rem;
    }

    .calculator-section {
        padding: 1.5rem;
    }

    .unit-toggle-group {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.75rem;
    }

    .unit-toggle .unit-option {
        padding: 0.6rem 1.2rem;
        font-size: 0.9rem;
    }

    .measurement-item {
        padding: 1rem;
    }

    nav ul {
        gap: 1rem;
    }

    .tools-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 1.75rem;
    }

    h2 {
        font-size: 1.5rem;
    }

    .calculator-section {
        padding: 1rem;
    }
}