/* ----- 全局重置与基础样式 (完全自研，不依赖外部库) ----- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, BlinkMacSystemFont, 'Roboto', 'Helvetica Neue', sans-serif;
    background-color: #f3f4f6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    line-height: 1.5;
    color: #1f2937;
}

/* 容器 max-w-7xl 风格 */
.container-custom {
    max-width: 80rem; /* 1280px -> 7xl */
    margin-left: auto;
    margin-right: auto;
    padding-left: 1rem;
    padding-right: 1rem;
    width: 100%;
}

/* 响应式 padding */
@media (min-width: 640px) {
    .container-custom {
        padding-left: 1.5rem;
        padding-right: 1.5rem;
    }
}
@media (min-width: 1024px) {
    .container-custom {
        padding-left: 2rem;
        padding-right: 2rem;
    }
}

/* 通用弹性布局 */
.flex-grow {
    flex-grow: 1;
}

/* 文本与间距工具 */
.text-center {
    text-align: center;
}
.mb-12 {
    margin-bottom: 3rem;
}
.mb-3 {
    margin-bottom: 0.75rem;
}
.mb-6 {
    margin-bottom: 1.5rem;
}
.mt-12 {
    margin-top: 3rem;
}
.py-12 {
    padding-top: 3rem;
    padding-bottom: 3rem;
}
.py-8 {
    padding-top: 2rem;
    padding-bottom: 2rem;
}
.px-4 {
    padding-left: 1rem;
    padding-right: 1rem;
}
.p-6 {
    padding: 1.5rem;
}
@media (min-width: 768px) {
    .p-6 {
        padding: 2rem;
    }
    .md\:p-8 {
        padding: 2rem;
    }
}

/* 排版 */
.text-3xl {
    font-size: 1.875rem;
    line-height: 2.25rem;
}
.text-2xl {
    font-size: 1.5rem;
    line-height: 2rem;
}
.font-extrabold {
    font-weight: 800;
}
.font-bold {
    font-weight: 700;
}
.text-gray-900 {
    color: #111827;
}
.text-gray-600 {
    color: #4b5563;
}
.text-gray-500 {
    color: #6b7280;
}
.leading-relaxed {
    line-height: 1.625;
}
h4 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-top: 1rem;
    margin-bottom: 0.5rem;
    color: #1e3a8a;
    border-left: 4px solid #3b82f6;
    padding-left: 0.75rem;
}
h4:first-of-type {
    margin-top: 0;
}

/* 卡片与过渡 */
.bg-white {
    background-color: #ffffff;
}
.rounded-xl {
    border-radius: 0.75rem;
}
.shadow-md {
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}
.overflow-hidden {
    overflow: hidden;
}
.transition-all {
    transition-property: all;
    transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
    transition-duration: 300ms;
}
.card-hover:hover {
    transform: translateY(-5px);
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}
.space-y-12 > * + * {
    margin-top: 3rem;
}

/* 视频容器 16:9 */
.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 */
    height: 0;
    overflow: hidden;
    border-radius: 0.5rem;
    background-color: #000000;
    margin-top: 1.5rem;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}
.video-container iframe,
.video-container video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
    object-fit: cover;
}
/* 多个视频间距微调 */
.video-container + .video-container {
    margin-top: 1.25rem;
}

/* footer */
.border-t {
    border-top-width: 1px;
    border-top-style: solid;
}
.border-gray-200 {
    border-color: #e5e7eb;
}
.flex {
    display: flex;
}
.justify-between {
    justify-content: space-between;
}
.items-center {
    align-items: center;
}
.flex-col {
    flex-direction: column;
}
@media (min-width: 768px) {
    .md\:flex-row {
        flex-direction: row;
    }
    .md\:mb-0 {
        margin-bottom: 0;
    }
}
.mb-4 {
    margin-bottom: 1rem;
}
.text-sm {
    font-size: 0.875rem;
}

/* 简单辅助样式 */
.w-full {
    width: 100%;
}
.shadow-lg {
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}
hr {
    margin: 1rem 0;
}