:root {
    --bg: #0f172a;
    --card: #ffffff;
    --text: #1e293b;
    --muted: #64748b;
    --border: #cbd5e1;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --success-bg: #dcfce7;
    --success-fg: #166534;
    --error-bg: #fee2e2;
    --error-fg: #991b1b;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    background: linear-gradient(180deg, #0f172a 0%, #1e293b 100%);
    color: var(--text);
    min-height: 100vh;
    padding: 24px 12px;
}

.container {
    max-width: 760px;
    margin: 0 auto;
    background: var(--card);
    border-radius: 14px;
    padding: 28px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.25);
}

.app-header h1 { margin: 0 0 4px; font-size: 1.5rem; }
.subtitle { margin: 0 0 20px; color: var(--muted); }

fieldset {
    border: 1px solid var(--border);
    border-radius: 10px;
    margin: 0 0 18px;
    padding: 16px;
}

legend { font-weight: 600; padding: 0 6px; color: var(--primary); }

.grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
}

.field { display: flex; flex-direction: column; gap: 6px; }
.field-wide { grid-column: 1 / -1; }
.field span { font-size: 0.85rem; font-weight: 600; }

input, select, textarea {
    font: inherit;
    padding: 9px 11px;
    border: 1px solid var(--border);
    border-radius: 8px;
    width: 100%;
    background: #fff;
    color: var(--text);
}

input:focus, select:focus, textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

input:disabled { background: #f1f5f9; color: var(--muted); }

textarea { resize: vertical; }

.checkbox {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 12px;
    font-size: 0.9rem;
}
.checkbox input { width: auto; }

.field-error {
    color: var(--error-fg);
    font-size: 0.8rem;
    font-weight: 500;
}

.actions { text-align: right; }

button {
    background: var(--primary);
    color: #fff;
    border: none;
    border-radius: 8px;
    padding: 11px 20px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
}
button:hover { background: var(--primary-hover); }

.alert {
    border-radius: 10px;
    padding: 14px 16px;
    margin-bottom: 16px;
    line-height: 1.45;
}
.alert-success { background: var(--success-bg); color: var(--success-fg); }
.alert-error { background: var(--error-bg); color: var(--error-fg); }
.alert-hint { margin: 8px 0 0; font-size: 0.88rem; }

.smtp-log {
    border: 1px solid var(--border);
    border-radius: 10px;
    margin-bottom: 18px;
    padding: 8px 12px;
}
.smtp-log summary { cursor: pointer; font-weight: 600; }
.smtp-log pre {
    background: #0f172a;
    color: #e2e8f0;
    padding: 12px;
    border-radius: 8px;
    overflow-x: auto;
    font-size: 0.8rem;
    white-space: pre-wrap;
    word-break: break-word;
}

.app-footer {
    margin-top: 18px;
    color: var(--muted);
    font-size: 0.8rem;
    text-align: center;
}

@media (max-width: 560px) {
    .grid { grid-template-columns: 1fr; }
    .container { padding: 18px; }
}