.auth-shell { min-height: calc(100vh - 145px); }
.auth-card { border-color: color-mix(in srgb, var(--primary), var(--line) 72%); box-shadow: var(--shadow-lg); }
.auth-card__intro { position: relative; overflow: hidden; background: radial-gradient(circle at 50% -15%, rgba(0, 214, 194, .22), transparent 45%), linear-gradient(180deg, var(--surface-2), var(--surface)); }
.auth-card__intro::after { content: ""; position: absolute; inset: auto 12% 0; height: 1px; background: linear-gradient(90deg, transparent, var(--primary), transparent); opacity: .65; }
.auth-brand-logo { width: 116px; height: 98px; margin-bottom: 10px; object-fit: contain; filter: drop-shadow(0 12px 18px rgba(0, 155, 142, .20)); }
.auth-error { border-color: color-mix(in srgb, var(--danger), transparent 60%); background: var(--danger-soft); color: var(--danger); }
html[data-theme="dark"] .signup-guide { border-color: var(--line); background: linear-gradient(145deg, var(--surface-2), var(--surface)); }
html[data-theme="dark"] .signup-guide ol { color: var(--muted); }
html[data-theme="dark"] .signup-guide p,
html[data-theme="dark"] .signup-security-note,
html[data-theme="dark"] .auth-result-note { border-color: color-mix(in srgb, var(--info), transparent 60%); background: var(--info-soft); color: var(--info); }
html[data-theme="dark"] .signup-review-warning { border-color: color-mix(in srgb, var(--warning), transparent 60%); background: var(--warning-soft); color: var(--warning); }