*{box-sizing:border-box}body{margin:0;background:#f2f5f9;font-family:Arial,sans-serif;color:#1f2937}.card{width:min(420px,92%);margin:8vh auto;background:#fff;padding:28px;border-radius:16px;box-shadow:0 8px 30px #0001}.card h1{text-align:center}.card p{text-align:center}.card a,.topbar a{color:#2563eb;text-decoration:none}label{display:block;margin:14px 0 6px;font-weight:bold}input{width:100%;padding:13px;border:1px solid #d1d5db;border-radius:10px;font-size:16px}button{border:0;background:#2563eb;color:#fff;padding:12px 18px;border-radius:10px;font-size:16px}.card button{width:100%;margin-top:20px}.error,.success{padding:11px;border-radius:9px;margin-bottom:12px}.error{background:#fee2e2;color:#991b1b}.success{background:#dcfce7;color:#166534}.page,.chat-page{max-width:800px;margin:auto;min-height:100vh;background:#fff}.topbar{display:flex;justify-content:space-between;align-items:center;padding:16px;border-bottom:1px solid #e5e7eb}.panel{padding:20px}.users{display:flex;flex-direction:column;gap:8px}.user{display:flex;align-items:center;gap:12px;padding:14px;border:1px solid #e5e7eb;border-radius:12px;color:#111827;text-decoration:none}.avatar{width:42px;height:42px;border-radius:50%;background:#2563eb;color:#fff;display:grid;place-items:center;font-weight:bold}.chat-page{display:flex;flex-direction:column}.messages{flex:1;min-height:calc(100vh - 130px);padding:16px;overflow-y:auto;background:#f8fafc}.msg{max-width:75%;padding:10px 13px;border-radius:14px;margin:8px 0;word-wrap:break-word}.msg small{display:block;opacity:.6;font-size:11px;margin-top:4px}.mine{margin-right:0;margin-left:auto;background:#dbeafe}.theirs{margin-left:0;margin-right:auto;background:#e5e7eb}.send-form{display:flex;gap:8px;padding:10px;border-top:1px solid #ddd}.send-form input{flex:1}.send-form button{width:90px}