body {
    font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at 20% 80%, rgba(120, 119, 198, 0.3) 0%, transparent 50%),
                radial-gradient(circle at 80% 20%, rgba(255, 255, 255, 0.1) 0%, transparent 50%);
    z-index: -1;
    animation: backgroundFloat 20s ease-in-out infinite;
}

@keyframes backgroundFloat {
    0%, 100% { transform: translateY(0px) rotate(0deg); }
    50% { transform: translateY(-20px) rotate(180deg); }
}

.main-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    animation: fadeInUp 1s ease-out;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.intro-card {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-radius: 30px;
    box-shadow: 
        0 25px 80px rgba(0,0,0,0.15),
        0 0 0 1px rgba(255,255,255,0.1),
        inset 0 1px 0 rgba(255,255,255,0.8);
    padding: 60px;
    max-width: 800px;
    text-align: center;
    position: relative;
    overflow: hidden;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.intro-card:hover {
    transform: translateY(-10px);
    box-shadow: 
        0 35px 100px rgba(0,0,0,0.2),
        0 0 0 1px rgba(255,255,255,0.2),
        inset 0 1px 0 rgba(255,255,255,0.9);
}

.intro-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 5px;
    background: linear-gradient(90deg, #667eea, #764ba2, #667eea);
    background-size: 200% 100%;
    animation: gradientShift 3s ease-in-out infinite;
}

@keyframes gradientShift {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

.intro-card::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: conic-gradient(
        transparent,
        rgba(102, 126, 234, 0.03),
        transparent,
        rgba(118, 75, 162, 0.03),
        transparent
    );
    animation: rotate 20s linear infinite;
    z-index: -1;
}

@keyframes rotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.profile-avatar {
    width: 160px;
    height: 160px;
    border-radius: 50%;
    border: 6px solid transparent;
    background: linear-gradient(135deg, #667eea, #764ba2);
    padding: 4px;
    margin-bottom: 30px;
    object-fit: cover;
    box-shadow: 
        0 15px 35px rgba(102, 126, 234, 0.4),
        0 5px 15px rgba(0, 0, 0, 0.1);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    animation: profileFloat 6s ease-in-out infinite;
    position: relative;
}

.profile-avatar:hover {
    transform: scale(1.05) rotateY(10deg);
    box-shadow: 
        0 25px 50px rgba(102, 126, 234, 0.5),
        0 10px 25px rgba(0, 0, 0, 0.15);
}

.profile-avatar::before {
    content: '';
    position: absolute;
    top: -6px;
    left: -6px;
    right: -6px;
    bottom: -6px;
    border-radius: 50%;
    background: linear-gradient(45deg, #667eea, #764ba2, #667eea);
    z-index: -1;
    animation: borderRotate 3s linear infinite;
}

@keyframes profileFloat {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-10px); }
}

@keyframes borderRotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.intro-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 15px;
    background: linear-gradient(135deg, #667eea, #764ba2, #667eea);
    background-size: 200% 100%;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: titleGradient 4s ease-in-out infinite;
    letter-spacing: -0.02em;
    text-shadow: 0 10px 20px rgba(102, 126, 234, 0.3);
}

@keyframes titleGradient {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

.intro-subtitle {
    font-size: 1.4rem;
    color: #6c757d;
    margin-bottom: 30px;
    font-weight: 500;
    animation: slideInFromLeft 1s ease-out 0.3s both;
    position: relative;
}

.intro-subtitle::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 2px;
    background: linear-gradient(90deg, #667eea, #764ba2);
    border-radius: 1px;
}

@keyframes slideInFromLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.intro-description {
    font-size: 1.15rem;
    color: #555;
    margin-bottom: 40px;
    line-height: 1.8;
    animation: fadeIn 1s ease-out 0.6s both;
    font-weight: 400;
}

.action-buttons {
    display: flex;
    gap: 25px;
    justify-content: center;
    flex-wrap: wrap;
    animation: slideInFromBottom 1s ease-out 0.9s both;
}

@keyframes slideInFromBottom {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.action-btn {
    padding: 18px 35px;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    font-size: 1.1rem;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    border: 2px solid transparent;
    min-width: 220px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(10px);
}

.action-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.4), transparent);
    transition: left 0.5s ease;
}

.action-btn:hover::before {
    left: 100%;
}

.btn-primary-custom {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: 2px solid transparent;
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.btn-primary-custom:hover {
    transform: translateY(-5px) scale(1.02);
    box-shadow: 
        0 15px 35px rgba(102, 126, 234, 0.4),
        0 5px 15px rgba(0, 0, 0, 0.1);
    color: white;
}

.btn-outline-custom {
    background: rgba(255, 255, 255, 0.1);
    color: #667eea;
    border: 2px solid #667eea;
    backdrop-filter: blur(10px);
}

.btn-outline-custom:hover {
    background: #667eea;
    color: white;
    transform: translateY(-5px) scale(1.02);
    box-shadow: 
        0 15px 35px rgba(102, 126, 234, 0.4),
        0 5px 15px rgba(0, 0, 0, 0.1);
}

.contact-info {
    margin-top: 40px;
    padding-top: 30px;
    border-top: 1px solid #eee;
}

.contact-item {
    display: inline-flex;
    align-items: center;
    margin: 0 15px;
    color: #6c757d;
    text-decoration: none;
    transition: color 0.3s ease;
}

.contact-item:hover {
    color: #667eea;
}

.contact-item i {
    margin-right: 8px;
    font-size: 1.1rem;
}

.language-toggle {
    position: fixed;
    top: 25px;
    right: 25px;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(20px);
    padding: 12px 18px;
    border-radius: 50px;
    box-shadow: 
        0 8px 25px rgba(0,0,0,0.1),
        0 0 0 1px rgba(255,255,255,0.2),
        inset 0 1px 0 rgba(255,255,255,0.3);
    display: flex;
    align-items: center;
    gap: 12px;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    animation: slideInFromTop 1s ease-out 0.5s both;
}

.language-toggle:hover {
    transform: translateY(-3px);
    background: rgba(255, 255, 255, 0.25);
    box-shadow: 
        0 15px 35px rgba(0,0,0,0.15),
        0 0 0 1px rgba(255,255,255,0.3),
        inset 0 1px 0 rgba(255,255,255,0.4);
}

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

.toggle-switch {
    position: relative;
    width: 65px;
    height: 32px;
    background: rgba(200, 200, 200, 0.6);
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: inset 0 2px 6px rgba(0,0,0,0.2);
}

.toggle-switch.active {
    background: linear-gradient(135deg, #667eea, #764ba2);
    box-shadow: 
        inset 0 2px 6px rgba(0,0,0,0.1),
        0 0 15px rgba(102, 126, 234, 0.4);
}

.toggle-slider {
    position: absolute;
    top: 3px;
    left: 3px;
    width: 26px;
    height: 26px;
    background: white;
    border-radius: 50%;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 
        0 3px 8px rgba(0,0,0,0.2),
        0 0 0 1px rgba(255,255,255,0.8);
}

.toggle-switch.active .toggle-slider {
    transform: translateX(33px);
    box-shadow: 
        0 3px 8px rgba(0,0,0,0.3),
        0 0 0 1px rgba(255,255,255,0.9),
        0 0 15px rgba(255,255,255,0.5);
}

.lang-label {
    font-weight: 700;
    font-size: 0.9em;
    color: rgba(255, 255, 255, 0.8);
    transition: all 0.3s ease;
    text-shadow: 0 1px 2px rgba(0,0,0,0.3);
}

.lang-label.active {
    color: white;
    text-shadow: 0 0 10px rgba(255,255,255,0.5);
    transform: scale(1.1);
}

/* Hide elements based on language */
.lang-vi { display: block !important; }
.lang-en { display: none !important; }

body.english .lang-vi { display: none !important; }
body.english .lang-en { display: block !important; }

@media (max-width: 768px) {
    .intro-card {
        padding: 40px 30px;
        margin: 10px;
    }
    
    .intro-title {
        font-size: 2rem;
    }
    
    .action-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .action-btn {
        min-width: auto;
        width: 100%;
        max-width: 300px;
    }
    
    .contact-info {
        margin-top: 30px;
    }
    
    .contact-item {
        display: block;
        margin: 10px 0;
    }
}