diff --git a/gallery/example1.pdf b/gallery/example1.pdf
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index 0000000..30c3a09
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diff --git a/gallery/example1.typ b/gallery/example1.typ
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+++ b/gallery/example1.typ
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+#import "/src/lib.typ" as chronos
+
+#chronos.from-plantuml(```plantuml
+Alice -> Bob: Authentication Request
+Bob --> Alice: Authentication Response
+
+Alice -> Bob: Another authentication Request
+Alice <-- Bob: Another authentication Response
+```)
+
+
+#chronos.diagram({
+  import "/src/diagram.typ": *
+  _seq("Alice", "Bob", comment: "Authentication Request")
+  _seq("Bob", "Alice", comment: "Authentication Response", style: "dashed")
+  
+  _seq("Alice", "Bob", comment: "Another authentication Request")
+  _seq("Bob", "Alice", comment: "Another authentication Response", style: "dashed")
+})
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diff --git a/src/diagram.typ b/src/diagram.typ
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+++ b/src/diagram.typ
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+#import "renderer.typ": render
+
+#let _seq(p1, p2, comment: none, style: auto) = {
+  return ((
+    type: "seq",
+    p1: p1,
+    p2: p2,
+    comment: comment,
+    style: style
+  ),)
+}
+
+#let _par(name, display-name: auto, start-at: 0) = {
+  return ((
+    type: "par",
+    name: name,
+    display-name: if display-name == auto {name} else {display-name},
+    start-at: start-at
+  ),)
+}
+
+#let _par-exists(participants, name) = {
+  for p in participants {
+    if name == p.name {
+      return true
+    }
+  }
+  return false
+}
+
+#let diagram(elements) = {
+  let participants = ()
+  for elmt in elements {
+    if elmt.type == "par" {
+      participants.push(elmt)
+    } else if elmt.type == "seq" {
+      if not _par-exists(participants, elmt.p1) {
+        participants.push(_par(elmt.p1).first())
+      }
+      if not _par-exists(participants, elmt.p2) {
+        participants.push(_par(elmt.p2).first())
+      }
+    }
+  }
+
+  render(participants, elements)
+}
+
+#let from-plantuml(code) = {
+  let code = code.text
+}
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diff --git a/src/lib.typ b/src/lib.typ
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index 0000000..2f20eb6
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+++ b/src/lib.typ
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+#import "diagram.typ": diagram, from-plantuml
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diff --git a/src/renderer.typ b/src/renderer.typ
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index 0000000..849d8ad
--- /dev/null
+++ b/src/renderer.typ
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+#import "@preview/cetz:0.2.2": canvas, draw
+
+#let X-SPACE = 2
+#let Y-SPACE = 30
+
+#let get-participants-i(participants) = {
+  let pars-i = (:)
+  for (i, p) in participants.enumerate() {
+    pars-i.insert(p.name, i)
+  }
+  return pars-i
+}
+
+#let get-columns-width(participants, elements) = {
+  let pars-i = get-participants-i(participants)
+  let cells = ()
+  for elmt in elements {
+    if elmt.type == "seq" {
+      let com = if elmt.comment == none {""} else {elmt.comment}
+      let i1 = pars-i.at(elmt.p1)
+      let i2 = pars-i.at(elmt.p2)
+      cells.push(
+        (
+          elmt: elmt,
+          i1: calc.min(i1, i2),
+          i2: calc.max(i1, i2),
+          cell: box(com, inset: 3pt)
+        )
+      )
+    }
+  }
+
+  let widths = participants.slice(0, -1).map(_ => 0)
+  for cell in cells.filter(c => c.i2 - c.i1 == 1) {
+    let m = measure(cell.cell)
+    widths.at(cell.i1) = calc.max(
+      widths.at(cell.i1),
+      m.width / 1pt
+    )
+  }
+  return widths
+}
+
+#let render(participants, elements) = context canvas(length: 1pt, {
+  let pars-i = get-participants-i(participants)
+
+  let widths = get-columns-width(participants, elements)
+
+  let x-pos = (0,)
+  for width in widths {
+    x-pos.push(x-pos.last() + width)
+  }
+  
+  // Draw participants
+  for (i, p) in participants.enumerate() {
+    draw.content(
+      (x-pos.at(i), 0),
+      p.display-name,
+      name: p.name,
+      frame: "rect",
+      padding: (5pt, 3pt),
+      anchor: "south"
+    )
+  }
+
+  let y = -Y-SPACE
+  // Draw sequences
+  for elmt in elements {
+    if elmt.type == "seq" {
+      let x1 = x-pos.at(pars-i.at(elmt.p1))
+      let x2 = x-pos.at(pars-i.at(elmt.p2))
+      draw.line(
+        (x1, y),
+        (x2, y),
+        mark: (end: "straight")
+      )
+      if elmt.comment != none {
+        draw.content(
+          (calc.min(x1, x2), y),
+          elmt.comment,
+          anchor: "south-west",
+          padding: 3pt
+        )
+      }
+      y -= Y-SPACE
+    }
+  }
+
+  // Draw vertical lines + end participants
+  draw.on-layer(-1, {
+    for (i, p) in participants.enumerate() {
+      let x = x-pos.at(i)
+      draw.line(
+        (x, 0),
+        (x, y),
+        stroke: (dash: "dashed", paint: gray.darken(40%))
+      )
+      draw.content(
+        (x, y),
+        p.display-name,
+        name: p.name,
+        frame: "rect",
+        padding: (5pt, 3pt),
+        anchor: "north"
+      )
+    }
+  })
+})
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diff --git a/typst.toml b/typst.toml
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index 0000000..e721a3c
--- /dev/null
+++ b/typst.toml
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+[package]
+name = "chronos"
+version = "0.0.1"
+compiler = "0.11.0"
+repository = "https://git.kb28.ch/HEL/chronos"
+entrypoint = "src/lib.typ"
+authors = [
+    "Louis Heredero <https://git.kb28.ch/HEL>"
+]
+categories = ["visualization"]
+license = "Apache-2.0"
+description = "A package to draw sequence diagrams with CeTZ"
+keywords = ["sequence", "diagram", "plantuml"]
+exclude = [ "/gallery/*" ]