// The project function defines how your document looks.
// It takes your content and some metadata and formats it.
// Go ahead and customize it to your liking!
#let project(title: "", subtitle: "", authors: (), logo: none, body) = {

  // Set the document's basic properties.
  set document(author: authors, title: title)
  set text(lang: "de")
  set heading(numbering: "1.1")

  set align(center)

  // Title page.
  v(1fr)
  
  // Logo
  if logo != none {
    image(logo, width: 50%)
  }
  v(3em)

  // Title
  text(2em, weight: 700, title)

  linebreak()
  v(0.1em)

  // Subtitle
  text(2em, weight: 400, subtitle)
  
  v(1em)

  // Author
  grid(
    ..authors,
  )

  v(1fr)
  pagebreak()

  set align(left)

  set page(numbering: "I", number-align: center)

  let ht-first = state("page-first-section", [])
  let ht-last = state("page-last-section", [])

  set page(
    header: {
      locate(loc => {
          // find first heading of level 1 on current page
          let first-heading = query(
            heading.where(level: 1), loc)
            .find(h => h.location().page() == loc.page())
          // find last heading of level 1 on current page
          let last-heading = query(
            heading.where(level: 1), loc)
            .rev()
            .find(h => h.location().page() == loc.page())
          // test if the find function returned none (i.e. no headings on this page)
          {
            if not first-heading == none {
              ht-first.update([
                // change style here if update needed section per section
                #first-heading.body
              ])
              ht-last.update([
                // change style here if update needed section per section
                #last-heading.body
              ])

              // if one or more headings on the page, use first heading
              // change style here if update needed page per page
              ht-first.display()
            } else {
              // no headings on the page, use last heading from variable
              // change style here if update needed page per page
              ht-last.display()
            }
          }
        }
      )

      v(-0.8em)
      line(length: 100%, stroke: 0.5pt)
    }
  )
  
  // Table of contents
  outline(depth: 3, indent: true)
  pagebreak()
  
  set page(numbering: "1")
  counter(page).update(1)

  // Main body
  set par(justify: true)

  body
}