/* ==============================================
 * common.css - 全站通用样式
 * ============================================== */

/* —— 布局容器 —— */
.container {
    width: 100%;
    max-width: var(--container-max);
    margin-left: auto;
    margin-right: auto;
    padding-left: var(--container-padding);
    padding-right: var(--container-padding);
}

/* —— 行内 flex 工具 —— */
.flex {
    display: flex;
}
.flex-center {
    display: flex;
    align-items: center;
    justify-content: center;
}
.flex-between {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

/* —— 通用按钮 —— */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: 12px 32px;
    border-radius: var(--radius-pill);
    font-size: var(--fs-md);
    font-weight: 600;
    line-height: 1;
    transition: transform var(--duration-base) var(--ease-out),
                box-shadow var(--duration-base) var(--ease-out),
                background-color var(--duration-base) var(--ease-out);
    white-space: nowrap;
    user-select: none;
}

.btn-primary {
    background: var(--gradient-tag);
    color: var(--color-text-on-accent);
    box-shadow: var(--shadow-tag);
}
.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 30px rgba(249, 115, 22, 0.4);
}
.btn-primary:active {
    transform: translateY(0);
}

.btn-outline {
    border: 2px solid rgba(255, 255, 255, 0.6);
    color: var(--color-text-on-primary);
    background: transparent;
}
.btn-outline:hover {
    background: rgba(255, 255, 255, 0.12);
    border-color: #fff;
}

.btn-purple {
    background: var(--color-primary);
    color: var(--color-text-on-primary);
    box-shadow: var(--shadow-md);
}
.btn-purple:hover {
    background: var(--color-primary-light);
    transform: translateY(-2px);
}

/* —— 区块 —— */
.section {
    padding: var(--space-20) 0;
}
.section-tight {
    padding: var(--space-16) 0;
}

/* —— 通用标题 —— */
.section-title {
    font-size: var(--fs-3xl);
    color: var(--color-text-primary);
    margin-bottom: var(--space-8);
    font-weight: 700;
    letter-spacing: 0.5px;
}

.section-title--orange {
    display: inline-block;
    background: var(--gradient-tag);
    color: var(--color-text-on-accent);
    padding: 14px 36px;
    border-radius: var(--radius-pill);
    font-size: var(--fs-md);
    box-shadow: var(--shadow-tag);
    margin: 0 auto;
}

/* —— 居中标签 —— */
.section-tagline {
    text-align: center;
    position: relative;
    margin: 0 auto var(--space-12);
    max-width: 720px;
}
.section-tagline::before,
.section-tagline::after {
    content: "";
    position: absolute;
    top: 50%;
    width: 30%;
    height: 1px;
    background: var(--gradient-divider);
}
.section-tagline::before { left: 0; }
.section-tagline::after { right: 0; }

/* —— 浮现动画 —— */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity var(--duration-slow) var(--ease-out),
                transform var(--duration-slow) var(--ease-out);
}
.reveal.is-visible {
    opacity: 1;
    transform: translateY(0);
}

/* —— 返回顶部按钮 —— */
.back-top {
    position: fixed;
    right: 32px;
    bottom: 32px;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-deep));
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    box-shadow: 0 12px 28px rgba(91, 91, 251, 0.4);
    z-index: var(--z-tooltip);
    opacity: 0;
    transform: translateY(20px);
    transition: opacity var(--duration-base), transform var(--duration-base);
    cursor: pointer;
}
.back-top.is-show {
    opacity: 1;
    transform: translateY(0);
    display: flex !important;
}
.back-top:hover {
    transform: translateY(-4px) scale(1.05);
}
.back-top::after {
    content: "↑";
    font-weight: 900;
}

/* —— 标签组件 —— */
@media (max-width: 1024px) {
    :root {
        --fs-4xl: 38px;
        --fs-5xl: 50px;
        --fs-3xl: 30px;
        --space-20: 64px;
        --space-16: 48px;
    }
}

@media (max-width: 768px) {
    .container {
        padding-left: 20px;
        padding-right: 20px;
    }
}

/* —— 全局a状态 —— */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}