diff --git a/src/bin/asteroids.rs b/src/bin/asteroids.rs
index e3ed65f..076ff93 100644
--- a/src/bin/asteroids.rs
+++ b/src/bin/asteroids.rs
@@ -2,8 +2,8 @@ use geo::algorithm::intersects::Intersects;
 use geo::algorithm::rotate::Rotate;
 use geo::prelude::Translate;
 use geo::rotate::RotatePoint;
+use geo::LineString;
 use geo::{Coordinate, MultiPolygon, Point, Polygon};
-use geo::{LineString};
 use geo_clipper::Clipper;
 use polygon_art::MultiPolygonExt;
 use polygon_art::{load_multipolgon_from_svg, Context};
@@ -14,15 +14,28 @@ fn main() {
     let mut context = Context::create();
     let mut rng = context.gen_rng();
 
-    let ship_width = 100.;
-    let center_point = MultiPolygon(vec![create_asteroid(&mut rng, 20, 2)])
-        .scale_to_width(2.5 * ship_width)
-        .translate(context.width / 2., context.height / 2.);
+    let width = context.width;
+    let height = context.height;
+    let diagonal = f64::sqrt(width * width + height * height);
+
+    // todo : it does not make to much sense to define all parameters like this
+    // todo : it makes more sense to create a static (diagonal / width /height ratio ) setup and scale it up
+    let frame_offset = diagonal * 0.01;
+    let max_asteroid = (diagonal / 40.) as usize;
+
+    let min_asteroid_size = diagonal / 40.;
+    let max_asteroid_size = diagonal / 12.;
+    let ship_length = diagonal / 23.;
+    let ship_orbit = 3.0;
+
+    let center_point = MultiPolygon(vec![create_asteroid(&mut rng, 8, 2)])
+        .scale_to_width(ship_orbit * ship_length)
+        .translate(width / 2., height / 2.);
 
     // create asteroid
     let mut asteroids: Vec<MultiPolygon<f64>> = Vec::new();
-    for _ in 0..40 {
-        let without_orbit = rng.gen_range(40..140) as f64;
+    for _ in 0..(max_asteroid * 2) {
+        let without_orbit = rng.gen_range(min_asteroid_size..max_asteroid_size) as f64;
         let with_orbit = without_orbit * 1.32;
         let x = rng.gen_range(0..(context.width as i32)) as f64;
         let y = rng.gen_range(0..(context.height as i32)) as f64;
@@ -30,14 +43,15 @@ fn main() {
             .scale_to_width(with_orbit)
             .translate(x, y);
 
-        if !center_point.intersects(&asteroid) && asteroids
-            .iter()
-            .find(|&m| *&m.intersects(&asteroid))
-            .is_none()
+        if (!center_point.intersects(&asteroid))
+            && asteroids
+                .iter()
+                .find(|&m| *&m.intersects(&asteroid))
+                .is_none()
         {
             asteroids.push(asteroid.scale_to_width(without_orbit));
         }
-        if asteroids.len() > 23 {
+        if asteroids.len() > max_asteroid {
             break;
         }
     }
@@ -46,7 +60,8 @@ fn main() {
     let rotation = rng.gen_range(0..360);
     let ship = load_multipolgon_from_svg("pool/asteroids/ship3.svg")
         .unwrap()
-        .scale_to_width(ship_width)
+        .rotate(90.) // rotate to scale ship with width
+        .scale_to_width(ship_length)
         .translate_center()
         .rotate(rotation as f64);
     context.translate_center();
@@ -54,8 +69,7 @@ fn main() {
     context.restore();
 
     // drawing and clipping
-    let frame_space = 10.;
-    let window = context.frame(frame_space, frame_space, frame_space, frame_space);
+    let window = context.frame(frame_offset, frame_offset, frame_offset, frame_offset);
     context.draw_polygon(&window);
 
     for asteroid in asteroids.iter() {
diff --git a/src/context.rs b/src/context.rs
index 8983be5..0919b70 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -91,12 +91,29 @@ impl Context {
     pub fn gen_rng(&mut self) -> StdRng {
         StdRng::seed_from_u64(self.pseudo_random_number_generator.gen())
     }
+
     pub fn create() -> Context {
         let opt = Opt::get_command_line_arguments();
-        let height = f64::from(opt.height.clone());
-        let width = f64::from(opt.width.clone());
         let line_size = opt.line_size.clone();
 
+        let mm = 3.779527547619048; // calculated with inkscape 1587.40157 (px) / 420 (mm) (from a3)
+        let (mut height, mut width) = match opt.format {
+            None => (f64::from(opt.height.clone()), f64::from(opt.width.clone())),
+            Some(format) => match &format[..] {
+                "a3" => (297. * mm, 420. * mm),
+                "a4" => (210. * mm, 297. * mm),
+                "a5" => (148. * mm, 210. * mm),
+                "x220" => (768., 1366.),
+                _ => (f64::from(opt.height.clone()), f64::from(opt.width.clone())),
+            },
+        };
+
+        if opt.orientation == "portrait" {
+            let cache = height;
+            height = width;
+            width = cache;
+        }
+
         let random_seed = match opt.random_seed {
             Some(random_seed) => random_seed,
             None => match opt.random_seed_date {
@@ -128,9 +145,8 @@ impl Context {
             .expect("Can't svg surface");
             Box::new(SvgRenderContainer::new(svg_surface, palette)) as Box<dyn RenderContainer>
         } else if opt.output_type == "png" {
-            let png_surface =
-                ImageSurface::create(Format::Rgb24, opt.width.clone(), opt.height.clone())
-                    .expect("Can't create png surface");
+            let png_surface = ImageSurface::create(Format::Rgb24, width as i32, height as i32)
+                .expect("Can't create png surface");
             Box::new(PngRenderContainer::new(
                 opt.output.to_string_lossy().to_string(),
                 png_surface,
diff --git a/src/context/commandline.rs b/src/context/commandline.rs
index f019227..b246a6c 100644
--- a/src/context/commandline.rs
+++ b/src/context/commandline.rs
@@ -13,13 +13,30 @@ pub struct Opt {
     pub output: PathBuf,
 
     /// define width in pixels
-    #[structopt(long, default_value = "400")]
+    #[structopt(long, default_value = "600")]
     pub width: i32,
 
     /// define height in pixels
     #[structopt(long, default_value = "400")]
     pub height: i32,
 
+    /// use a predefined format
+    #[structopt(
+        long,
+        conflicts_with="height",
+        conflicts_with="width",
+        possible_values=&["a3", "a4", "a5", "x220"]
+    )]
+    pub format: Option<String>,
+
+    /// change orientation
+    #[structopt(
+        long,
+        default_value="landscape",
+        possible_values=&["portrait", "landscape"]
+    )]
+    pub orientation: String,
+
     /// define line size in pixels, all lines will be this thick
     #[structopt(long, default_value = "1.0")]
     pub line_size: f64,