#let callout(kind: str, label: str, body) = context if target() == "html" {
  html.section(class: kind + " callout", context {
    let depth = counter(heading).at(here()).len() + 1
    heading(
      depth: depth,
      outlined: false,
      numbering: none,
      label,
    )
    " "
    body
  })
} else {
  let col = (
    note: color.rgb("#0000cd"),
    warn: color.rgb("#a52a2a"),
    tip: color.rgb("#228b22"),
    todo: color.rgb("#ff0000"),
    eg: auto,
  ).at(kind)
  block(
    fill: if (col != auto) {col.transparentize(85%)} else {auto},
    stroke: (y: col),
    width: 100%,
    outset: (x: 1em, y: 0.5em),
    spacing: par.spacing + 0.5em,
    inset: (y: 0.5em),
    {
      set text(fill: col)
      strong(label)
      body
    },
  )
}


#let note = callout.with(kind: "note", label: "Note:")
#let warn = callout.with(kind: "warn", label: "Warning:")
#let tip = callout.with(kind: "tip", label: "Tip:")

// #let todo = callout.with(kind: "todo", label: "TODO:")
#let todo(caption, ..args) = callout(kind: "todo", label: "TODO:", {
  show figure: none
  (
    caption,
    figure(kind: "todo", supplement: "TODO", caption: caption, none),
    ..args.pos(),
  ).join(parbreak())
})


#let example = callout.with(kind: "eg", label: "For example:")

#let details(body, label: "Details", open: false) = {
  context if target() == "html" {
    html.details(open: open, {
      html.summary(strong[Click for #label])
      body
    })
  } else {
    [
      #strong(label):
      #body
    ]
  }
}

// #let solution = details.with(label: "Solution")
#let solution = callout.with(kind: "solution", label: "Solution:")