如何在Shiny中将一个CSS元素放在另一个元素下居中

ui <- fluidPage(
  tags$div(
    id = "container",
    style = "position: relative;",
    # 其他内容
  )
)

ui <- fluidPage(
  tags$div(
    id = "container",
    style = "position: relative;",
    tags$div(
      id = "centered-element",
      style = "position: absolute; top: 50%;",
      # 其他内容
    )
  )
)

ui <- fluidPage(
  tags$div(
    id = "container",
    style = "position: relative;",
    tags$div(
      id = "centered-element",
      style = "position: absolute; top: 50%; transform: translateX(-50%);",
      # 其他内容
    )
  )
)