/* Design System Variables - Premium Red, Black & White */
:root {
    --primary-color: #D90429; /* Crimson Red */
    --hover-color: #EF233C; /* Bright Red */
    --bg-color: #F8F9FA; /* Snow White background */
    --text-main: #1D1D1D; /* Deep Black for text */
    --text-muted: #6C757D;
    --white: #FFFFFF;
    --black: #0B090A;
    --border-radius: 8px; /* Sharper edges for a sleek modern feel */
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg-color);
    color: var(--text-main);
    line-height: 1.7;
}

/* ==== Header & Tabs ==== */
header {
    background: linear-gradient(135deg, var(--black) 0%, #400000 100%);
    padding: 70px 20px 0;
    text-align: center;
    color: var(--white);
    border-bottom: 4px solid var(--primary-color);
}

.header-content h1 {
    font-size: 3.5rem;
    font-weight: 900;
    margin-bottom: 10px;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.header-subtitle {
    font-size: 1.15rem;
    color: #ADB5BD;
    margin-bottom: 50px;
    font-weight: 400;
    letter-spacing: 0.05em;
}

.tabs {
    display: flex;
    justify-content: center;
    gap: 12px;
    padding-bottom: 25px;
}

.tab-btn {
    display: inline-block;
    text-decoration: none;
    background: transparent;
    border: 1px solid rgba(255, 255, 255, 0.2);
    color: var(--white);
    padding: 12px 30px;
    cursor: pointer;
    border-radius: 4px;
    font-size: 1.05rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    transition: var(--transition);
}

.tab-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
    border-color: rgba(255, 255, 255, 0.4);
}

.tab-btn.active {
    background: var(--primary-color);
    color: var(--white);
    border-color: var(--primary-color);
    box-shadow: 0 4px 15px rgba(217, 4, 41, 0.5);
}

/* ==== Main Content ==== */
main {
    max-width: 900px;
    margin: 50px auto;
    padding: 0 20px;
}

.tab-content {
    background: var(--white);
    padding: 50px;
    border-radius: var(--border-radius);
    box-shadow: 0 8px 30px -5px rgba(0, 0, 0, 0.1);
    animation: fadeIn 0.5s ease-out;
    border-top: 5px solid var(--black);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ==== Typography & Elements ==== */
h2 {
    font-size: 2.3rem;
    font-weight: 800;
    color: var(--black);
    margin-bottom: 30px;
    position: relative;
    padding-bottom: 15px;
    text-transform: uppercase;
}

h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 80px;
    height: 4px;
    background: var(--primary-color);
}

h3 {
    font-size: 1.4rem;
    margin: 40px 0 20px;
    color: var(--black);
    font-weight: 700;
    text-transform: uppercase;
}

p {
    margin-bottom: 25px;
    color: var(--text-muted);
    font-size: 1.15rem;
}

strong {
    color: var(--black);
    font-weight: 700;
}

em {
    color: var(--primary-color);
    font-style: italic;
}

.highlight {
    background: var(--black);
    padding: 3px 10px;
    border-radius: 3px;
    color: var(--white);
    font-weight: 700;
}

/* ==== Lists ==== */
.tour-list {
    list-style: none;
}

.tour-list li {
    padding: 18px 25px;
    margin-bottom: 15px;
    background: var(--white);
    border: 1px solid #E9ECEF;
    border-radius: var(--border-radius);
    border-left: 6px solid var(--black);
    transition: var(--transition);
}

.tour-list li:hover {
    transform: translateX(10px);
    border-left-color: var(--primary-color);
    box-shadow: 0 5px 15px rgba(0,0,0,0.05);
}

/* ==== Video ==== */
.video-container {
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    margin-top: 30px;
    border: 2px solid var(--black);
    position: relative;
}

video {
    width: 100%;
    display: block;
}

/* ==== Table ==== */
.table-container {
    overflow-x: auto;
    border-radius: var(--border-radius);
    box-shadow: 0 8px 20px rgba(0,0,0,0.08);
    margin: 30px 0;
    border: 1px solid #E9ECEF;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--white);
}

th {
    background: var(--black);
    color: var(--white);
    padding: 22px;
    text-align: left;
    font-weight: 700;
    font-size: 1.1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

td {
    padding: 20px;
    border-bottom: 1px solid #E9ECEF;
    font-size: 1.1rem;
    color: var(--black);
}

tr:last-child td {
    border-bottom: none;
}

tr:hover td {
    background: #F8F9FA;
}

.price {
    font-weight: 800;
    color: var(--primary-color);
}

/* ==== Gallery ==== */
.gallery {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.gallery img {
    width: 100%;
    height: 280px;
    object-fit: cover;
    border-radius: var(--border-radius);
    transition: var(--transition);
    border: 3px solid transparent;
}

.gallery img:hover {
    transform: scale(1.05);
    border-color: var(--primary-color);
    box-shadow: 0 15px 35px rgba(0,0,0,0.2);
}

/* ==== Responsive ==== */
@media (max-width: 768px) {
    .header-content h1 { font-size: 2.5rem; }
    .tabs { flex-wrap: wrap; padding: 0 15px 25px; }
    .tab-btn { flex: 1 1 calc(50% - 15px); text-align: center; padding: 12px; }
    .tab-content { padding: 35px 20px; }
}

/* ==== Footer ==== */
footer {
    background: var(--black);
    color: var(--white);
    text-align: center;
    padding: 30px 20px;
    margin-top: 50px;
    border-top: 3px solid var(--primary-color);
}

footer p {
    margin-bottom: 5px;
    color: #ADB5BD;
    font-size: 1.05rem;
}

footer strong {
    color: var(--white);
    letter-spacing: 0.05em;
    font-size: 1.15rem;
}

/* ==== Form Đăng Ký ==== */
.register-form {
    background: var(--white);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid #E9ECEF;
    margin-top: 30px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 700;
    color: var(--black);
}

.form-group input, 
.form-group select {
    width: 100%;
    padding: 12px 15px;
    border: 1px solid #CED4DA;
    border-radius: 6px;
    font-family: inherit;
    font-size: 1rem;
    transition: var(--transition);
}

.form-group input:focus, 
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(217, 4, 41, 0.1);
}

.submit-btn {
    display: inline-block;
    width: 100%;
    background: var(--primary-color);
    color: var(--white);
    padding: 15px;
    border: none;
    border-radius: 6px;
    font-size: 1.15rem;
    font-weight: 800;
    text-transform: uppercase;
    cursor: pointer;
    transition: var(--transition);
}

.submit-btn:hover {
    background: var(--hover-color);
    box-shadow: 0 5px 15px rgba(217, 4, 41, 0.3);
    transform: translateY(-2px);
}

.success-message {
    margin-top: 25px;
    background: #D1E7DD;
    color: #0F5132;
    padding: 15px 20px;
    border-radius: 6px;
    border-left: 5px solid #198754;
    font-weight: 600;
    animation: fadeIn 0.4s ease-out;
}