:root{--sf-bg:#f7f7f7;--sf-text:#111;--sf-muted:#555;--sf-border:#ddd;--sf-primary:#111;--sf-primary-text:#fff;--sf-card-bg:#fff;--sf-card-shadow:0 4px 12px #0000000f}html,body{background:var(--sf-bg);color:var(--sf-text);margin:0;padding:0;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;line-height:1.6}h1,h2,h3{margin:0 0 .5rem;font-weight:600}p{margin:.5rem 0 1rem}button{cursor:pointer;transition:opacity .2s}button:hover{opacity:.85}.container{max-width:900px;margin:0 auto;padding:0 2rem}.sf-card{background:var(--sf-card-bg);box-shadow:var(--sf-card-shadow);border-radius:12px;padding:1.5rem}