* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Noto Sans SC", "Segoe UI", sans-serif;
}

body {
    background: linear-gradient(135deg, #f0f7ff 0%, #e6f0ff 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    color: #1d2129;
}

#header {
    position: absolute;
    top: 20px;
    left: 20px;
}

.container {
    width: 100%;
    max-width: 1200px;
    background: white;
    border-radius: 20px;
    box-shadow: 0 15px 50px rgba(0, 80, 180, 0.15);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 25px 40px;
    background: white;
    border-bottom: 1px solid #f0f2f5;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    width: 42px;
    height: 42px;
    background: linear-gradient(135deg, #3370ff, #165dff);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 24px;
    font-weight: bold;
}

.logo-text {
    font-size: 28px;
    font-weight: 800;
    color: #165dff;
}

.nav-links {
    display: flex;
    gap: 35px;
}

.nav-links a {
    text-decoration: none;
    color: #4e5969;
    font-weight: 500;
    font-size: 16px;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: #165dff;
}

.nav-btn {
    background: #f2f3f5;
    padding: 10px 20px;
    border-radius: 8px;
    font-weight: 500;
}

.nav-btn:hover {
    background: #e5e6eb;
}

.hero {
    display: flex;
    padding: 40px;
    gap: 50px;
}

.content {
    flex: 1;
    padding: 30px 0;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.tagline {
    font-size: 14px;
    font-weight: 600;
    color: #3370ff;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 15px;
}

h1 {
    font-size: 48px;
    line-height: 1.2;
    margin-bottom: 20px;
    color: #1d2129;
}

h1 span {
    color: #3370ff;
}

.subtitle {
    font-size: 20px;
    color: #4e5969;
    margin-bottom: 30px;
    font-weight: 500;
    max-width: 550px;
    line-height: 1.6;
}

.features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-bottom: 40px;
}

.feature {
    display: flex;
    align-items: flex-start;
    gap: 12px;
}

.feature-icon {
    background: #ebf2ff;
    width: 36px;
    height: 36px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #3370ff;
}

.feature-text {
    flex: 1;
    color: #1d2129;
}

.feature-text h3 {
    font-size: 18px;
    margin-bottom: 5px;
    color: #1d2129;
}

.feature-text p {
    font-size: 14px;
    color: #86909c;
}

.download-area {
    display: flex;
    flex-direction: column;
    gap: 15px;
    max-width: 500px;
}

.btn-download {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    background: linear-gradient(135deg, #3370ff, #165dff);
    color: white;
    font-size: 20px;
    font-weight: 600;
    padding: 20px 40px;
    border-radius: 15px;
    text-decoration: none;
    box-shadow: 0 10px 25px rgba(51, 112, 255, 0.35);
    transition: all 0.3s ease;
    border: none;
    cursor: pointer;
}

.btn-download:hover {
    transform: translateY(-3px);
    box-shadow: 0 15px 30px rgba(51, 112, 255, 0.45);
}

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

.os-options {
    display: flex;
    gap: 15px;
}

.os-btn {
    flex: 1;
    background: white;
    border: 2px solid #e5e6eb;
    border-radius: 12px;
    padding: 15px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
}

.os-btn:hover {
    border-color: #3370ff;
}

.os-btn.active {
    border-color: #3370ff;
    background: #f0f6ff;
}

.os-btn i {
    font-size: 24px;
    margin-bottom: 10px;
    color: #3370ff;
}

.os-btn p {
    font-size: 14px;
    color: #4e5969;
    font-weight: 500;
}

.info-text {
    font-size: 14px;
    color: #86909c;
    margin-top: 10px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.product-image {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
}

.product-image * {
    cursor: default;
}

.app-window {
    width: 100%;
    max-width: 500px;
    background: white;
    border-radius: 20px;
    box-shadow: 0 25px 50px rgba(0, 0, 0, 0.15);
    overflow: hidden;
    position: relative;
    z-index: 2;
    border: 1px solid #e5e6eb;
}

.app-content {
    display: flex;
    height: 100%;
}

.sidebar {
    width: 70px;
    background: #f7f8fa;
    padding: 20px 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 25px;
}

.sidebar-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 5px;
    color: #86909c;
    font-size: 12px;
    cursor: pointer;
}

.sidebar-item.active {
    color: #3370ff;
}

.sidebar-icon {
    width: 36px;
    height: 36px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: white;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.05);
}

.sidebar-item.active .sidebar-icon {
    background: #ebf2ff;
    color: #3370ff;
}

.main-content {
    flex: 1;
    padding: 25px;
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.chat-header {
    display: flex;
    align-items: center;
    gap: 12px;
    padding-bottom: 15px;
    border-bottom: 1px solid #f0f2f5;
}

.avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: linear-gradient(135deg, #3370ff, #165dff);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
}

.chat-info h3 {
    font-size: 16px;
    color: #1d2129;
}

.chat-info p {
    font-size: 13px;
    color: #86909c;
}

.messages {
    display: flex;
    flex-direction: column;
    gap: 15px;
    flex: 1;
}

.message {
    max-width: 80%;
    padding: 12px 16px;
    border-radius: 12px;
    font-size: 14px;
    line-height: 1.5;
}

.message-received {
    background: #f0f2f5;
    align-self: flex-start;
    border-bottom-left-radius: 4px;
}

.message-sent {
    background: #ebf2ff;
    align-self: flex-end;
    border-bottom-right-radius: 4px;
}

.input-area {
    display: flex;
    gap: 10px;
    padding-top: 15px;
    border-top: 1px solid #f0f2f5;
}

.input-box {
    flex: 1;
    background: #f7f8fa;
    border-radius: 8px;
    padding: 12px 15px;
    font-size: 14px;
    color: #4e5969;
}

.send-btn {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    background: #3370ff;
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}

.decoration {
    position: absolute;
    z-index: 1;
}

.decoration-1 {
    width: 200px;
    height: 200px;
    background: linear-gradient(135deg, rgba(51, 112, 255, 0.15), rgba(22, 93, 255, 0.1));
    border-radius: 50%;
    top: -30px;
    right: -30px;
}

.decoration-2 {
    width: 150px;
    height: 150px;
    background: linear-gradient(135deg, rgba(51, 112, 255, 0.1), rgba(22, 93, 255, 0.05));
    border-radius: 30px;
    bottom: -30px;
    left: -30px;
    transform: rotate(45deg);
}

.footer {
    text-align: center;
    padding: 25px;
    background: #f7f8fa;
    color: #86909c;
    font-size: 14px;
    border-top: 1px solid #e5e6eb;
}

.footer a {
    color: #3370ff;
    text-decoration: none;
}

@media (max-width: 900px) {
    .hero {
        flex-direction: column;
    }

    .content {
        align-items: center;
        text-align: center;
    }

    .features {
        grid-template-columns: 1fr;
    }

    .download-area {
        align-items: center;
    }

    .product-image {
        margin-top: 30px;
    }

    .subtitle {
        text-align: center;
    }
}