:root{--bg:#0f172a;--card:#111827;--text:#e5e7eb;--muted:#9ca3af;--primary:#60a5fa;--accent:#34d399}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica,Arial,sans-serif}
.header{padding:16px;border-bottom:1px solid #1f2937}
.header h1{margin:0;font-size:20px}
.container{max-width:980px;margin:0 auto;padding:16px}
.tabs{display:flex;gap:8px;margin-bottom:12px}
.tab{padding:10px 14px;background:#1f2937;color:var(--text);border:none;border-radius:8px;cursor:pointer}
.tab.active{background:var(--primary);color:#001}
.panel{display:none;padding:16px;background:var(--card);border-radius:12px}
.panel.active{display:block}
.form{display:grid;grid-template-columns:1fr;gap:12px}
.field{display:flex;flex-direction:column;gap:6px}
.field span{color:var(--muted);font-size:14px}
textarea{width:100%;padding:10px;border-radius:8px;border:1px solid #374151;background:#0b1220;color:var(--text)}
input[type=file]{padding:6px;border-radius:8px;border:1px dashed #374151;background:#0b1220;color:var(--text)}
.btn{display:inline-block;padding:10px 14px;background:var(--accent);color:#001;border:none;border-radius:8px;cursor:pointer;text-decoration:none}
.result{margin-top:12px}
.result.hidden{display:none}
#encrypt-preview{max-width:100%;height:auto;border-radius:8px;border:1px solid #1f2937}
.text{white-space:pre-wrap;word-break:break-word;background:#0b1220;border:1px solid #374151;border-radius:8px;padding:12px}
@media (min-width: 900px){
  .form{grid-template-columns:1fr 1fr}
  .form .field:nth-child(1){grid-column:1 / span 2}
}