* {
    box-sizing: border-box;
}

body {
    min-height: 100vh;
    background: linear-gradient(135deg, #74ebd5 0%, #ACB6E5 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 10px;
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
}

.main-container {
    width: 100%;
    max-width: 420px;
    margin: 0 auto;
}

/* Phần intro icons */
.intro-section {
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(15px);
    border-radius: 20px;
    padding: 20px 15px;
    margin-bottom: 25px;
    border: 1px solid rgba(255, 255, 255, 0.25);
    box-shadow: 0 8px 32px rgba(31, 38, 135, 0.2);
}

.intro-item {
    text-align: center;
    transition: transform 0.3s ease;
    position: relative;
    padding: 10px 5px;
}

.intro-item:hover {
    transform: translateY(-5px);
}

.intro-item .step-number {
    position: absolute;
    top: 8px;
    right: 8px;
    background: rgba(116, 235, 213, 0.9);
    color: white;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: bold;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    border: 2px solid white;
    z-index: 10;
}

.intro-icon {
    width: 80px;
    height: 80px;
    object-fit: contain;
    margin-bottom: 12px;
    filter: drop-shadow(0 4px 12px rgba(0, 0, 0, 0.15));
    background: rgba(255, 255, 255, 0.8);
    border-radius: 50%;
    padding: 2px;
}

.intro-caption {
    font-size: 0.75rem;
    font-weight: 600;
    color: #2c3e50;
    margin: 0;
    line-height: 1.4;
    white-space: pre-line;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Card đăng nhập */
.card {
    border-radius: 25px;
    box-shadow: 0 20px 40px rgba(31, 38, 135, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.2);
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(15px);
    padding: 2rem;
}

.card h2 {
    color: #2c3e50;
    font-weight: 700;
    margin-bottom: 30px;
    font-size: 2rem;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.form-control {
    border-radius: 15px;
    border: 2px solid #e9ecef;
    padding: 15px 20px;
    transition: all 0.3s ease;
    font-size: 1rem;
    background: rgba(255, 255, 255, 0.9);
}

.form-control:focus {
    border-color: #74ebd5;
    box-shadow: 0 0 0 0.25rem rgba(116, 235, 213, 0.25);
    transform: translateY(-2px);
    background: white;
    color: #212529;
}

.form-label {
    font-weight: 600;
    color: #495057;
    margin-bottom: 10px;
    font-size: 0.95rem;
}

.btn-custom {
    background: linear-gradient(135deg, #74ebd5 0%, #4fc3f7 100%);
    color: #fff;
    border-radius: 15px;
    padding: 15px;
    font-weight: 600;
    transition: all 0.3s ease;
    border: none;
    font-size: 1.1rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.btn-custom:hover {
    background: linear-gradient(135deg, #4fc3f7 0%, #74ebd5 100%);
    color: #fff;
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(116, 235, 213, 0.4);
}

.btn-custom:active {
    transform: translateY(-1px);
}

.register-link {
    color: #6c757d;
    font-size: 0.9rem;
    text-decoration: none;
    display: block;
    margin-top: 25px;
    text-align: center;
    transition: all 0.3s ease;
    font-weight: 500;
    flex: 1;
}

.register-link:hover {
    color: #4fc3f7;
    text-decoration: underline;
}

.checkbox label {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.9rem;
    color: #6c757d;
    font-weight: 500;
}

.form-check-input {
    margin: 0;
}

/* Responsive */
/* Mobile First - Extra Small devices (phones, 576px and down) */
@media (max-width: 575.98px) {
    body {
        padding: 5px;
    }

    .main-container {
        max-width: 100%;
    }

    .intro-section {
        padding: 15px 10px;
        margin-bottom: 15px;
        border-radius: 15px;
    }

    .intro-item {
        padding: 5px 2px;
    }

    .intro-icon {
        width: 60px;
        height: 60px;
        /*padding: 8px;*/
    }

    .intro-item .step-number {
        top: 0px;
        right: 10px;
        width: 20px;
        height: 20px;
        font-size: 0.7rem;
        border: 1px solid white;
    }

    .intro-caption {
        font-size: 0.7rem;
        line-height: 1.2;
    }

    .card {
        padding: 1.5rem;
        border-radius: 20px;
    }

    .card h2 {
        font-size: 1.75rem;
        margin-bottom: 25px;
    }

    .form-control {
        padding: 12px 16px;
        border-radius: 12px;
        font-size: 0.95rem;
    }

    .btn-custom {
        padding: 12px;
        font-size: 1rem;
        border-radius: 12px;
    }

    .register-link {
        font-size: 0.85rem;
        margin-top: 20px;
    }
}

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) and (max-width: 767.98px) {
    .main-container {
        max-width: 540px;
    }

    .intro-icon {
        width: 70px;
        height: 70px;
    }

    .intro-caption {
        font-size: 0.8rem;
    }

    .card h2 {
        font-size: 1.85rem;
    }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) and (max-width: 991.98px) {
    .main-container {
        max-width: 500px;
    }

    .intro-section {
        padding: 25px 20px;
    }

    .intro-icon {
        width: 90px;
        height: 90px;
    }

    .intro-caption {
        font-size: 0.9rem;
    }

    .card {
        padding: 2.5rem;
    }

    .card h2 {
        font-size: 2.1rem;
    }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) {
    .main-container {
        max-width: 450px;
    }

    .intro-section {
        padding: 30px 25px;
    }

    .intro-icon {
        width: 100px;
        height: 100px;
    }

    .card {
        padding: 3rem;
    }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
    .main-container {
        max-width: 480px;
    }
}

/* Landscape orientation for mobile */
@media (max-height: 500px) and (orientation: landscape) {
    body {
        padding: 5px;
    }

    .intro-section {
        margin-bottom: 10px;
        padding: 10px;
    }

    .intro-icon {
        width: 50px;
        height: 50px;
    }

    .intro-caption {
        font-size: 0.65rem;
    }

    .card {
        padding: 1rem;
    }

    .card h2 {
        font-size: 1.5rem;
        margin-bottom: 15px;
    }

    .form-control {
        padding: 10px 15px;
    }

    .btn-custom {
        padding: 10px;
    }
}

/* High DPI displays */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    .intro-icon {
        image-rendering: -webkit-optimize-contrast;
        image-rendering: crisp-edges;
    }
}

/* Animation cho load trang */
.intro-section, .card {
    animation: fadeInUp 0.6s ease-out forwards;
    opacity: 0;
}

.card {
    animation-delay: 0.2s;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Accessibility improvements */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    .card {
        background: rgba(40, 44, 52, 0.95);
        color: #e9ecef;
    }

    .card h2 {
        color: #f8f9fa;
    }

    .form-label {
        color: #ced4da;
    }

    .form-control {
        background: rgba(255, 255, 255, 0.1);
        border-color: rgba(255, 255, 255, 0.2);
        color: #f8f9fa;
    }

    .form-control::placeholder {
        color: rgba(255, 255, 255, 0.6);
    }

    .form-control:focus {
        background: rgba(255, 255, 255, 0.15);
        color: #f8f9fa;
    }

    .checkbox label {
        color: #ced4da;
    }

    .register-link {
        color: #adb5bd;
    }

    .intro-caption {
        color: #f8f9fa;
    }
}

/* Print styles */
@media print {
    body {
        background: white !important;
    }

    .card {
        box-shadow: none !important;
        border: 1px solid #ccc !important;
    }
}