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

:root {
    --primary-dark: #000000;
    --primary-blue: #0ea5e9;
    --text-dark: #1f2937;
    --text-light: #6b7280;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    height: 100vh;
    overflow: hidden;
    background: #f9fafb;

}

.container {
    display: flex;
    height: 100vh;
}

/* Welcome Section - Left Side */
.welcome-section {
    flex: 1;
    background: linear-gradient(135deg, #000000 0%, #0c0c0c 60%, #1e3a8a 85%, #0ea5e9 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    position: relative;
    overflow: hidden;
}

.welcome-section::before {
    content: '';
    position: absolute;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(14, 165, 233, 0.15) 1px, transparent 1px);
    background-size: 50px 50px;
    animation: moveBackground 20s linear infinite;
    opacity: 0.5;
}

@keyframes moveBackground {
    0% {
        transform: translate(0, 0);
    }

    100% {
        transform: translate(50px, 50px);
    }
}

.welcome-content {
    position: relative;
    z-index: 1;
    text-align: center;
    padding: 40px;
    max-width: 500px;
    animation: fadeInUp 0.8s ease-out;
}

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

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

.logo {
    margin-bottom: 30px;
    animation: float 3s ease-in-out infinite;
}

@keyframes float {

    0%,
    100% {
        transform: translateY(0);
    }

    50% {
        transform: translateY(-10px);
    }
}

.logo i {
    font-size: 90px;
    opacity: 0.95;
    filter: drop-shadow(0 10px 20px rgba(0, 0, 0, 0.3));
}

.welcome-content h1 {
    font-size: 28px;
    font-weight: 400;
    margin-bottom: 10px;
    opacity: 0.95;
    letter-spacing: 0.5px;
}

.welcome-content h2 {
    font-size: 56px;
    font-weight: 800;
    margin-bottom: 20px;
    letter-spacing: -1px;
    background: linear-gradient(to right, #ffffff, #0ea5e9);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.tagline {
    font-size: 18px;
    opacity: 0.9;
    margin-bottom: 50px;
    font-weight: 300;
}

.features {
    display: flex;
    flex-direction: column;
    gap: 20px;
    align-items: flex-start;
    margin: 0 auto;
    max-width: 320px;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 15px;
    font-size: 16px;
    padding: 12px 20px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 12px;
    backdrop-filter: blur(10px);
    width: 100%;
    transition: all 0.3s ease;
}

.feature-item:hover {
    background: rgba(255, 255, 255, 0.15);
    transform: translateX(10px);
}

.feature-item i {
    font-size: 22px;
    color: #0ea5e9;
    filter: drop-shadow(0 0 10px rgba(14, 165, 233, 0.5));
}

/* Login Section - Right Side */
.login-section {
    flex: 1;
    background: white;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px;
    box-shadow: -5px 0 20px rgba(0, 0, 0, 0.05);
}

.login-content {
    width: 100%;
    max-width: 420px;
    animation: fadeInRight 0.8s ease-out;
}

@keyframes fadeInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }

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

.login-content h3 {
    font-size: 36px;
    color: var(--text-dark);
    margin-bottom: 12px;
    font-weight: 700;
    letter-spacing: -0.5px;
}

.subtitle {
    color: var(--text-light);
    font-size: 16px;
    margin-bottom: 50px;
    font-weight: 400;
}

.login-buttons {
    display: flex;
    flex-direction: column;
    gap: 18px;
    margin-bottom: 30px;
}

.social-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 14px;
    padding: 18px 28px;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-md);
    position: relative;
    overflow: hidden;
}

.social-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
    transition: left 0.5s;
}

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

.social-btn:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-xl);
}

.social-btn:active {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.social-btn i {
    font-size: 22px;
}

.google-btn {
    background: white;
    color: var(--text-dark);
    border: 2px solid var(--border-color);
}

.google-btn:hover {
    background: #f9fafb;
    border-color: #d1d5db;
}

.google-btn i {
    color: #4285f4;
}

.facebook-btn {
    background: linear-gradient(135deg, #1877f2 0%, #0e5fc7 100%);
    color: white;
    border: 2px solid transparent;
}

.facebook-btn:hover {
    background: linear-gradient(135deg, #166fe5 0%, #0d52ab 100%);
}

.terms {
    text-align: center;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
}

.terms p {
    font-size: 13px;
    color: var(--text-light);
    line-height: 1.7;
}

.terms a {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.2s ease;
}

.terms a:hover {
    text-decoration: underline;
    color: #0284c7;
}

.divider {
    display: flex;
    align-items: center;
    text-align: center;
    margin: 30px 0;
}

.divider::before,
.divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid var(--border-color);
}

.divider span {
    padding: 0 20px;
    color: var(--text-light);
    font-size: 14px;
    font-weight: 500;
}

.home-link {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    padding: 14px 28px;
    background: transparent;
    color: var(--text-dark);
    text-decoration: none;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 15px;
    font-weight: 500;
    transition: all 0.3s ease;
    margin-bottom: 20px;
}

.home-link:hover {
    background: #f9fafb;
    border-color: var(--primary-blue);
    color: var(--primary-blue);
    transform: translateY(-2px);
}

.home-link i {
    font-size: 18px;
}

/* Responsive Design */
@media (max-width: 968px) {
    .container {
        flex-direction: column;
    }

    .welcome-section {
        flex: 0.4;
    }

    .login-section {
        flex: 0.6;
    }

    .welcome-content h1 {
        font-size: 24px;
    }

    .welcome-content h2 {
        font-size: 36px;
    }

    .features {
        display: none;
    }
}

/* @media (max-width: 640px) {
    .welcome-section {
    
        display: none;
    }

    .login-section {
        flex: 1;
    }
} */
@media (max-width: 640px) {
    body {
        margin: 0;
        padding: 0;
        height: 100vh;
        display: flex;
        justify-content: center;
        align-items: center;
    }

    .container {
        display: flex;
        flex-direction: column;
        /* 2 khối xếp cột */
        justify-content: flex-start;
        /* căn từ trên, không dư trống nhiều */
        align-items: center;
        height: 100vh;
        width: 100%;
        padding: 0;
        box-sizing: border-box;
    }

    .welcome-section {
        flex: 0 0 30%;
        /* chiếm 40% container height */
        width: 100%;
        max-width: 400px;
        display: flex;
        flex-direction: column;
        justify-content: center;
        align-items: center;
        padding: 1vh 0;
        box-sizing: border-box;
    }

    .login-section {
        flex: 0 0 70%;
        /* chiếm 60% container height */
        width: 100%;
        max-width: 400px;
        display: flex;
        flex-direction: column;
        justify-content: flex-start;
        align-items: center;
        padding: 20px;
        box-sizing: border-box;
    }

    /* Scale font theo viewport width */
    .welcome-content h1 {
        font-size: 4vw;
        max-font-size: 26px;
        text-align: center;
        margin-bottom: 0.5vh;
    }

    .welcome-content h2 {
        font-size: 7vw;
        max-font-size: 36px;
        text-align: center;
        margin-bottom: 1vh;
    }

    .welcome-content .tagline {
        margin: 0;
    }

    .login-content .subtitle {
        margin-bottom: 20px;
    }

    .login-content h3 {
        font-size: 5.5vw;
        max-font-size: 30px;
        text-align: center;
        margin-bottom: 1vh;
    }
    .login-content .login-buttons {
        margin-bottom: 20px;
    }
    .login-content .divider {
        margin: 20px 0;
    }
    .login-content .terms {
        margin-top: 20px;
    }

    .login-buttons {
        gap: 1.5vh;
    }

    .features {
        display: none;
    }
}