:root {
    --primary-color: #4361ee;
    --primary-dark: #3a56d4;
    --success-color: #06d6a0;
    --warning-color: #ffd166;
    --danger-color: #ef476f;
    --text-primary: #2b2d42;
    --text-secondary: #8d99ae;
    --bg-light: #f8f9fa;
    --bg-white: #ffffff;
    --border-color: #edf2f4;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    --radius: 12px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg-light);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 20px;
    min-height: 100vh;
}

.app-container {
    max-width: 900px;
    margin: 0 auto;
}

/* Header */
.app-header {
    text-align: center;
    margin-bottom: 2.5rem;
    padding-top: 1.5rem;
}
.app-header h1 {
    font-size: 2.8rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
}
.tagline {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Card nhập liệu */
.input-card {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}
.input-card label {
    display: block;
    font-weight: 600;
    margin-bottom: 1rem;
    font-size: 1.1rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}
.input-group {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
}
#domain-input {
    flex: 1;
    padding: 1rem 1.25rem;
    font-size: 1.1rem;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    transition: all 0.3s ease;
    font-family: 'Inter', sans-serif;
}
#domain-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.15);
}
#check-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    white-space: nowrap;
}
#check-btn:hover { background: var(--primary-dark); }
.input-hint {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-top: 0.5rem;
}

/* Các trạng thái: Loading, Error, Result */
.status-card {
    text-align: center;
    padding: 3rem 2rem;
    border-radius: var(--radius);
    margin-bottom: 2rem;
    display: none;
}
.loading { background: var(--bg-white); box-shadow: var(--shadow); }
.error { background: #fff5f5; color: var(--danger-color); border: 1px solid #ffcccc; }
.error h3 { margin: 1rem 0 0.5rem; }
.spinner {
    width: 50px; height: 50px;
    border: 4px solid var(--border-color);
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    margin: 0 auto 1.5rem;
    animation: spin 1s linear infinite;
}
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }

/* Khu vực kết quả */
.result-area { display: none; }
.result-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    gap: 1rem;
}
.result-header h2 { font-size: 1.5rem; font-weight: 600; }
.target-domain { color: var(--primary-color); word-break: break-all; }
.status-badge {
    padding: 0.5rem 1.25rem;
    border-radius: 50px;
    font-weight: 600;
    font-size: 0.95rem;
}
.status-badge.valid { background: #e7faf4; color: var(--success-color); }
.status-badge.expiring { background: #fff9e6; color: #e6b000; }
.status-badge.expired { background: #ffe6eb; color: var(--danger-color); }

/* Lưới thông tin */
.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}
.info-box {
    background: var(--bg-white);
    padding: 1.75rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}
.info-box h3 {
    font-size: 1.2rem;
    margin-bottom: 1.25rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}
.info-row {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.9rem;
    padding-bottom: 0.9rem;
    border-bottom: 1px dashed var(--border-color);
}
.info-row:last-child { border-bottom: none; margin-bottom: 0; }
.info-row.highlight { background: #f0f7ff; padding: 0.9rem; border-radius: 8px; }
.issuer-info {
    background: #f8f9fa;
    padding: 0.9rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
    word-break: break-word;
}

/* Chi tiết nâng cao */
.advanced-details {
    background: var(--bg-white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
    overflow: hidden;
}
.advanced-details summary {
    padding: 1.25rem 1.75rem;
    font-weight: 600;
    cursor: pointer;
    list-style: none;
    display: flex;
    align-items: center;
    justify-content: space-between;
    color: var(--primary-color);
}
.advanced-details summary::-webkit-details-marker { display: none; }
.advanced-details[open] summary i { transform: rotate(180deg); }
.advanced-details summary i { transition: transform 0.3s ease; }
.details-content { padding: 0 1.75rem 1.75rem; }
.details-content .info-row { border-bottom: none; padding-bottom: 0.75rem; }
.details-content code {
    background: #f1f3f9;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-size: 0.9em;
    word-break: break-word;
    text-align: right;
    display: inline-block;
    max-width: 70%;
}

/* Cảnh báo và nút */
.alert {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    padding: 1.25rem;
    border-radius: var(--radius);
    margin-top: 1.5rem;
}
.alert.warning { background: #fff9e6; border-left: 4px solid var(--warning-color); }
.alert i { font-size: 1.5rem; flex-shrink: 0; }
.btn-secondary {
    background: var(--bg-white);
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
    padding: 0.8rem 1.5rem;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    margin-top: 1rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.3s ease;
}
.btn-secondary:hover {
    background: var(--primary-color);
    color: white;
}

/* Footer */
.app-footer {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-top: 3rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}
.small-text { font-size: 0.85rem; margin-top: 0.5rem; }

/* Responsive */
@media (max-width: 768px) {
    body { padding: 15px; }
    .app-header h1 { font-size: 2.2rem; }
    .input-group { flex-direction: column; }
    #check-btn { justify-content: center; }
    .result-header { flex-direction: column; align-items: flex-start; }
    .info-grid { grid-template-columns: 1fr; }
    .info-row { flex-direction: column; gap: 0.3rem; }
    .details-content code { max-width: 100%; text-align: left; }
}
@media (max-width: 480px) {
    .app-header h1 { font-size: 1.8rem; flex-direction: column; gap: 0.5rem; }
    .input-card, .info-box { padding: 1.5rem; }
}