:root{--primary-color:#3498db;--secondary-color:#2980b9;--text-color:#333;--light-gray:#f5f5f5;--medium-gray:#e0e0e0;--dark-gray:#777;--white:#fff;--max-width:1200px;--border-radius:8px;--box-shadow:0 4px 6px rgba(0, 0, 0, 0.1);--transition:all 0.3s ease}*{margin:0;padding:0;box-sizing:border-box}body{font-family:'Segoe UI',Tahoma,Geneva,Verdana,sans-serif;line-height:1.6;color:var(--text-color);background-color:var(--light-gray);padding:0;margin:0}.back-link{color:#fff;text-decoration:none;display:inline-block;margin:10px 0;transition:var(--transition);font-size:20px;background-color:var(--primary-color);padding:8px 16px;border-radius:var(--border-radius);box-shadow:var(--box-shadow)}.back-link:hover{color:#fff;text-decoration:none;background-color:var(--secondary-color);transform:translateY(-2px)}.back-link i{margin-right:8px}header{background-color:var(--primary-color);color:var(--white);padding:1rem 0;box-shadow:var(--box-shadow)}.container{max-width:var(--max-width);margin:0 auto;padding:0 2rem}header .container{display:flex;justify-content:space-between;align-items:center}header h1{font-size:1.8rem;margin:0}header nav a{color:var(--white);text-decoration:none;margin-left:1.5rem;font-weight:500;transition:var(--transition)}header nav a:hover{opacity:.8}section{max-width:var(--max-width);margin:2rem auto;padding:2rem;background-color:var(--white);border-radius:var(--border-radius);box-shadow:var(--box-shadow)}h1{color:var(--primary-color);margin-bottom:1.5rem;font-size:2.2rem;border-bottom:2px solid var(--medium-gray);padding-bottom:.5rem}h2{color:var(--secondary-color);margin:2rem 0 1rem;font-size:1.8rem}h3{color:var(--secondary-color);margin:1.5rem 0 .8rem;font-size:1.4rem}h4{color:var(--text-color);margin:1.2rem 0 .6rem;font-size:1.2rem}p{margin-bottom:1rem;font-size:1rem;line-height:1.7}ul,ol{margin-bottom:1.5rem;padding-left:2rem}li{margin-bottom:.5rem}strong{color:var(--secondary-color)}a{color:var(--primary-color);text-decoration:none;transition:var(--transition)}a:hover{color:var(--secondary-color);text-decoration:underline}p:first-of-type{color:var(--dark-gray);font-style:italic;margin-bottom:1.5rem}ul li p{margin-bottom:.3rem}@media (max-width:768px){header .container{flex-direction:column;text-align:center;padding:1rem}header nav{margin-top:1rem}header nav a{margin:0 .75rem}section{padding:1.5rem;margin:1rem}h1{font-size:1.8rem}h2{font-size:1.5rem}}footer{background-color:var(--primary-color);color:var(--white);text-align:center;padding:1.5rem 0;margin-top:2rem}footer p{margin:0;font-size:.9rem}.back-to-top{position:fixed;bottom:2rem;right:2rem;background-color:var(--primary-color);color:var(--white);width:3rem;height:3rem;border-radius:50%;display:flex;justify-content:center;align-items:center;text-decoration:none;box-shadow:var(--box-shadow);opacity:0;transition:var(--transition);z-index:99}.back-to-top.visible{opacity:1}.back-to-top:hover{background-color:var(--secondary-color);transform:translateY(-3px)}header h1{font-family:'Arial Black',sans-serif;font-size:2rem;background:linear-gradient(to right,#3498db,#2c3e50);-webkit-background-clip:text;background-clip:text;color:#fff0;text-shadow:1px 1px 2px rgb(0 0 0 / .1)}