#let pgcounter = context [
  real page: #here().page() / #counter(page).final().first()
];
#set page(
  paper: "presentation-16-9",
  fill: rgb("222"),
  footer: align(center, pgcounter),
)
#set text(fill: white)

#let s_topic = state("topic", (color: red));
#let seite(n) = [#page(
    background: context {
      import "@preview/cetz:0.3.2"

      let pages = query(selector(<seite>).before(query(selector(<seite>).after(here())).first().location()))
      let last = counter(<seite>).final().first()
      let size = 100 / last

      [
        #place(
          bottom + left,
          stack(dir: ltr, ..pages.map(pg => {
            let seg_start = ((counter(<seite>).at(pg.location()).first() + 1) / last) * 100 - 50;
            link(pg.location(), box(width: size * 1%, height: 0.5%))
          }),)
        )
        #place(
          bottom + left,
          cetz.canvas(
            length: 1%,
            {
              import cetz.draw: *
              for pg in pages.rev() {
                let seg_start = ((counter(<seite>).at(pg.location()).first() + 1) / last) * 100 - 50
                rect((seg_start - size - 0.1, 0), (seg_start, 0.5), fill: s_topic.at(pg.location()).color, stroke: none)
              }
            },
          ),
        )
      ]
    },
  )[#lorem(n * 20)
    #align(bottom)[#text(size: 4em)[Slide #n]
    ]
  ] <seite>];

#let s = state("foo", "bar");














#for i in (1, 2, 3, 4) {
  seite(i)
}
#s_topic.update((color: blue))
#for i in (5, 6, 7) {
  seite(i)
}
#page[= miau 1]
#page[= miau 2]
#s_topic.update((color: green))
#for i in (8, 9) {
  seite(i)
}
#page[= miau 3]
#s_topic.update((color: yellow))
#for i in (10, 11, 12) {
  seite(i)
}

#text(context s.get())