/* ── 登录/注册页 login.php ── */
body {
    display: flex; flex-direction: column;
    align-items: center; justify-content: center; padding: 20px;
}
.card {
    background: var(--surface); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 40px 36px;
    width: 100%; max-width: 420px;
}
.logo { text-align: center; margin-bottom: 28px; }
.logo h1 {
    font-size: 1.6rem; font-weight: 700;
    background: linear-gradient(135deg, #6366f1, #a78bfa);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.logo p { color: var(--text-muted); font-size: 0.85rem; margin-top: 4px; }

.tabs { display: flex; border-bottom: 1px solid var(--border); margin-bottom: 24px; }
.tab {
    flex: 1; text-align: center; padding: 10px;
    cursor: pointer; font-size: 0.9rem; color: var(--text-muted);
    text-decoration: none; border-bottom: 2px solid transparent; transition: all 0.2s;
}
.tab.active { color: var(--primary); border-bottom-color: var(--primary); }

.form-group { margin-bottom: 16px; }
label { display: block; font-size: 0.85rem; color: var(--text-muted); margin-bottom: 6px; }
input[type="text"], input[type="email"], input[type="password"] {
    width: 100%; padding: 10px 14px;
    background: var(--bg); border: 1px solid var(--border);
    color: var(--text); border-radius: 8px; font-size: 0.9rem; outline: none;
    transition: border-color 0.2s;
}
input:focus { border-color: var(--primary); }

.btn {
    width: 100%; padding: 11px;
    background: var(--primary); color: #fff;
    border: none; border-radius: 8px; font-size: 0.95rem;
    font-weight: 600; cursor: pointer; transition: background 0.2s; margin-top: 8px;
}
.btn:hover { background: var(--primary-hover); }

.alert { padding: 10px 14px; border-radius: 8px; font-size: 0.85rem; margin-bottom: 16px; }
.alert-error   { background: rgba(239,68,68,0.12); color: var(--error); }
.alert-success { background: rgba(34,197,94,0.12); color: var(--success); }

.back-link { text-align: center; margin-top: 20px; font-size: 0.85rem; color: var(--text-muted); }
.back-link a { color: var(--primary); text-decoration: none; }
.back-link a:hover { text-decoration: underline; }