:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    --accent-color: #764ba2;
    --accent-hover: #5a3a8a;
    --text-primary: #2d3436;
    --text-secondary: #636e72;
    --glass-bg: rgba(255, 255, 255, 0.95);
    --glass-border: rgba(255, 255, 255, 0.2);
    --shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.15);
    --radius: 20px;
    --font-main: 'Inter', system-ui, -apple-system, sans-serif;
}

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

body {
    font-family: var(--font-main);
    background: var(--secondary-gradient);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    color: var(--text-primary);
    line-height: 1.6;
}

header {
    width: 100%;
    padding: 20px;
    display: flex;
    justify-content: center;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border);
    position: sticky;
    top: 0;
    z-index: 100;
}

.return-btn {
    text-decoration: none;
    color: white;
    background: var(--primary-gradient);
    padding: 10px 20px;
    border-radius: 50px;
    font-weight: 600;
    font-size: 0.9rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.return-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(118, 75, 162, 0.3);
}

main {
    flex: 1;
    width: 100%;
    max-width: 800px;
    padding: 40px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.converter-card {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 40px;
    width: 100%;
    box-shadow: var(--shadow);
    margin-bottom: 40px;
}

h1 {
    font-size: 2rem;
    font-weight: 800;
    margin-bottom: 30px;
    text-align: center;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.input-section {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 20px;
    align-items: center;
    margin-bottom: 30px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

input {
    width: 100%;
    padding: 15px;
    border: 2px solid #edf2f7;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 500;
    transition: border-color 0.3s ease, box-shadow 0.3s ease;
    outline: none;
}

input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 4px rgba(118, 75, 162, 0.1);
}

.actions {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    margin-top: 20px;
}

.swap-btn {
    background: #edf2f7;
    border: none;
    width: 45px;
    height: 45px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    transition: background 0.3s ease, transform 0.3s ease;
}

.clear-btn {
    background: #fef2f2;
    color: #ef4444;
    border: 1px solid #fee2e2;
    padding: 6px 15px;
    border-radius: 8px;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.clear-btn:hover {
    background: #fee2e2;
    transform: scale(1.05);
}

.swap-btn:hover {
    background: #e2e8f0;
    transform: rotate(180deg);
}

.result-area {
    background: #f8fafc;
    border-radius: 15px;
    padding: 25px;
    text-align: center;
    border: 1px dashed #cbd5e0;
}

.result-label {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.result-value {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--accent-color);
}

.result-unit {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-left: 5px;
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    width: 100%;
}

.info-card {
    background: var(--glass-bg);
    border-radius: 15px;
    padding: 25px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

.info-card h2 {
    font-size: 1.25rem;
    margin-bottom: 15px;
    color: var(--accent-color);
}

.info-card p,
.info-card li {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.info-card ul {
    list-style-type: none;
}

.info-card li::before {
    content: "📐";
    margin-right: 10px;
}

.adsense-container {
    margin-top: 40px;
    width: 100%;
    display: flex;
    justify-content: center;
    min-height: 250px;
    background: rgba(255, 255, 255, 0.5);
    border-radius: 10px;
    align-items: center;
    color: var(--text-secondary);
    font-style: italic;
    font-size: 0.8rem;
}

.seo-article-container {
    background: var(--glass-bg);
    border-radius: var(--radius);
    padding: 60px;
    margin-top: 40px;
    box-shadow: var(--shadow);
    width: 100%;
}

.seo-article-container h2 {
    font-size: 1.8rem;
    margin: 40px 0 20px;
    color: var(--accent-color);
}

.seo-article-container h2:first-of-type {
    margin-top: 0;
}

.seo-article-container h3 {
    font-size: 1.4rem;
    margin: 30px 0 15px;
    color: #4a5568;
}

.seo-article-container p {
    margin-bottom: 20px;
    font-size: 1.05rem;
    color: #4a5568;
    line-height: 1.8;
}

.seo-article-container img {
    max-width: 100%;
    height: auto;
    border-radius: 15px;
    margin: 30px 0;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.seo-article-container ol {
    margin: 20px 0 25px 25px;
}

.seo-article-container li {
    margin-bottom: 12px;
    font-size: 1.05rem;
    color: #4a5568;
}

.seo-article-container a {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 600;
}

.seo-article-container a:hover {
    text-decoration: underline;
}

footer {
    padding: 40px 20px;
    color: var(--text-secondary);
    font-size: 0.85rem;
    text-align: center;
    width: 100%;
}

@media (max-width: 600px) {
    .input-section {
        grid-template-columns: 1fr;
    }

    .actions {
        flex-direction: row;
        justify-content: center;
        margin: 10px auto;
    }

    .swap-btn {
        margin: 0;
        transform: rotate(90deg);
    }

    .swap-btn:hover {
        transform: rotate(270deg);
    }

    .converter-card {
        padding: 25px;
    }

    h1 {
        font-size: 1.5rem;
    }
}