diff --git a/internal/app/app.go b/internal/app/app.go
new file mode 100644
index 0000000..100ada7
--- /dev/null
+++ b/internal/app/app.go
@@ -0,0 +1,211 @@
+package app
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"bspviz/internal/bsp"
+	"bspviz/internal/geom"
+	"bspviz/internal/mapfmt"
+	"bspviz/internal/viz"
+	"bspviz/internal/wad"
+)
+
+type Options struct {
+	WadPath   string
+	MapMarker string
+	ListOnly  bool
+	Info      bool
+	Extract   []string
+	OutDir    string
+	GeomTest  bool
+	BuildBSP  bool
+	Alpha     float64
+	Beta      float64
+	Eps       float64
+	LeafMax   int
+	MaxDepth  int
+	Cands     int
+	Seed      int64
+	DotOut    string
+	TreePNG   string
+	Overlay   string
+}
+
+func Run(opts Options) error {
+	if strings.TrimSpace(opts.WadPath) == "" {
+		return fmt.Errorf("wad path required")
+	}
+
+	w, err := wad.Open(opts.WadPath)
+	if err != nil {
+		return fmt.Errorf("open wad: %w", err)
+	}
+	defer w.Close()
+
+	if opts.ListOnly {
+		fmt.Printf("WAD: %s\n", opts.WadPath)
+		for i, d := range w.Dir() {
+			fmt.Printf("%3d: %-8s size=%-7d pos=%-8d\n", i, d.Name(), d.Size, d.FilePos)
+		}
+		return nil
+	}
+
+	start, end, err := w.FindMap(opts.MapMarker)
+	if err != nil {
+		return fmt.Errorf("find map: %w", err)
+	}
+	fmt.Printf("Map %s: Directory [%d, %d)\n", strings.ToUpper(opts.MapMarker), start, end)
+
+	if opts.Info {
+		lumps, err := w.LoadMapLumps(opts.MapMarker, "VERTEXES", "LINEDEFS")
+		if err != nil {
+			return fmt.Errorf("load map lumps: %w", err)
+		}
+		vb := lumps["VERTEXES"]
+		lb := lumps["LINEDEFS"]
+		m, err := mapfmt.LoadMap(lumps)
+		if err != nil {
+			return err
+		}
+
+		verts := len(vb) / 4
+		lines := len(lb) / 14
+		fmt.Printf("VERTEXES: bytes=%d  count=%d\n", len(vb), verts)
+		fmt.Printf("LINEDEFS: bytes=%d  count=%d\n", len(lb), lines)
+
+		fmt.Printf("Map has %d vertices and %d linedefs\n", len(m.Vertices), len(m.Linedefs))
+		fmt.Printf("First vertex: %+v\n", m.Vertices[0])
+		fmt.Printf("First linedef: %+v\n", m.Linedefs[0])
+
+		if len(vb)%4 != 0 {
+			fmt.Println("WARN: VERTEXES size ist kein Vielfaches von 4 → Format prüfen")
+		}
+		if len(lb)%14 != 0 {
+			fmt.Println("WARN: LINEDEFS size ist kein Vielfaches von 14 → Format prüfen")
+		}
+	}
+
+	if len(opts.Extract) > 0 {
+		lumps, err := w.LoadMapLumps(opts.MapMarker, opts.Extract...)
+		if err != nil {
+			return fmt.Errorf("extract: %w", err)
+		}
+		if err := os.MkdirAll(opts.OutDir, 0o755); err != nil {
+			return fmt.Errorf("mkdir %s: %w", opts.OutDir, err)
+		}
+		for name, data := range lumps {
+			dst := filepath.Join(opts.OutDir, fmt.Sprintf("%s.lmp", name))
+			if err := os.WriteFile(dst, data, 0o644); err != nil {
+				return fmt.Errorf("write %s: %w", dst, err)
+			}
+			fmt.Printf("wrote %s (%d bytes)\n", dst, len(data))
+		}
+	}
+
+	if opts.GeomTest {
+		raw, err := w.LoadMapLumps(opts.MapMarker, "VERTEXES", "LINEDEFS")
+		if err != nil {
+			return fmt.Errorf("load map lumps: %w", err)
+		}
+		m, err := mapfmt.LoadMap(raw)
+		if err != nil {
+			return fmt.Errorf("parse map: %w", err)
+		}
+
+		segs := mapfmt.LinedefsToSegs(m.Vertices, m.Linedefs)
+		fmt.Printf("GEOM: vertices=%d linedefs=%d segs=%d\n", len(m.Vertices), len(m.Linedefs), len(segs))
+		if len(segs) == 0 {
+			fmt.Println("GEOM: keine Segmente gefunden – prüfe LINEDEFS/VERTEXES")
+			return nil
+		}
+
+		pts := make([]geom.Vec, 0, len(m.Vertices))
+		for _, v := range m.Vertices {
+			pts = append(pts, geom.V(float64(v.X), float64(v.Y)))
+		}
+		bb := geom.Bounds(pts)
+		w := bb.Max.X - bb.Min.X
+		h := bb.Max.Y - bb.Min.Y
+		fmt.Printf("AABB: min=(%.1f,%.1f) max=(%.1f,%.1f) size=(%.1f×%.1f)\n",
+			bb.Min.X, bb.Min.Y, bb.Max.X, bb.Max.Y, w, h)
+
+		O := segs[0].A
+		D := geom.Sub(segs[0].B, segs[0].A)
+		if geom.Len(D) < 1e-9 && len(segs) > 1 {
+			O = segs[1].A
+			D = geom.Sub(segs[1].B, segs[1].A)
+		}
+		var left, right, splits, degens int
+		for _, s := range segs {
+			f, b := geom.SplitSeg(s, O, D)
+			if len(f) == 0 && len(b) == 0 {
+				degens++
+				continue
+			}
+			left += len(f)
+			right += len(b)
+			if len(f) > 0 && len(b) > 0 {
+				splits++
+			}
+		}
+		fmt.Printf("PROBE-SPLIT: O=(%.1f,%.1f) D=(%.1f,%.1f)\n", O.X, O.Y, D.X, D.Y)
+		fmt.Printf("PROBE-SPLIT: left=%d right=%d splits=%d degens=%d (EPS=%.1e)\n",
+			left, right, splits, degens, geom.EPS)
+
+		return nil
+	}
+
+	if opts.BuildBSP {
+		raw, err := w.LoadMapLumps(opts.MapMarker, "VERTEXES", "LINEDEFS")
+		if err != nil {
+			return fmt.Errorf("load map lumps: %w", err)
+		}
+		m, err := mapfmt.LoadMap(raw)
+		if err != nil {
+			return fmt.Errorf("parse map: %w", err)
+		}
+
+		segs := mapfmt.LinedefsToSegs(m.Vertices, m.Linedefs)
+		p := bsp.Params{
+			Alpha: opts.Alpha, Beta: opts.Beta, Eps: opts.Eps,
+			MaxDepth: opts.MaxDepth, LeafMax: opts.LeafMax, Cands: opts.Cands, Seed: opts.Seed,
+		}
+		root := bsp.Build(segs, p)
+		st := bsp.Measure(root)
+
+		fmt.Printf("BSP built.\n")
+		fmt.Printf("  nodes=%d leaves=%d maxDepth=%d totalLeafSegs=%d\n",
+			st.Nodes, st.Leaves, st.MaxDepth, st.TotalSegs)
+		fmt.Printf("  params: alpha=%.2f beta=%.2f eps=%.1e leafMax=%d maxDepth=%d cands=%d seed=%d\n",
+			p.Alpha, p.Beta, p.Eps, p.LeafMax, p.MaxDepth, p.Cands, p.Seed)
+
+		if opts.DotOut != "" {
+			if err := viz.EmitDOT(root, opts.DotOut); err != nil {
+				return fmt.Errorf("write DOT: %w", err)
+			}
+			fmt.Printf("DOT export geschrieben: %s\n", opts.DotOut)
+
+			if opts.TreePNG != "" {
+				if err := viz.RunGraphviz(opts.DotOut, opts.TreePNG); err != nil {
+					log.Printf("Graphviz fehlgeschlagen: %v", err)
+				} else {
+					fmt.Printf("Graphviz PNG gebaut: %s\n", opts.TreePNG)
+				}
+			}
+		}
+
+		if opts.Overlay != "" {
+			if err := viz.RenderPNG(m, root, opts.Overlay); err != nil {
+				return fmt.Errorf("write overlay PNG: %w", err)
+			}
+			fmt.Printf("Overlay PNG geschrieben: %s\n", opts.Overlay)
+		}
+		return nil
+	}
+
+	return nil
+}
diff --git a/main.go b/main.go
index 57cd91f..8ce7c30 100644
--- a/main.go
+++ b/main.go
@@ -1,16 +1,12 @@
 package main
 
 import (
-	"bspviz/internal/bsp"
+	"bspviz/internal/app"
 	"bspviz/internal/geom"
-	"bspviz/internal/mapfmt"
-	"bspviz/internal/viz"
-	"bspviz/internal/wad"
 	"flag"
 	"fmt"
 	"log"
 	"os"
-	"path/filepath"
 	"strings"
 )
 
@@ -49,178 +45,41 @@ func main() {
 		usageAndExit("Flag -wad fehlt. Bitte Pfad zu einer Doom-kompatiblen WAD-Datei angeben.", 2)
 	}
 
-	w, err := wad.Open(*wadPath)
-	if err != nil {
-		log.Fatalf("open wad: %v", err)
-	}
-	defer w.Close()
-
-	if *listOnly {
-		fmt.Printf("WAD: %s\n", *wadPath)
-		for i, d := range w.Dir() {
-			fmt.Printf("%3d: %-8s size=%-7d pos=%-8d\n", i, d.Name(), d.Size, d.FilePos)
-		}
-		return
-	}
-
-	start, end, err := w.FindMap(*mapMarker)
-	if err != nil {
-		log.Fatalf("find map: %v", err)
-	}
-	fmt.Printf("Map %s: Directory [%d, %d)\n", strings.ToUpper(*mapMarker), start, end)
-
-	//info über die daten in WAD
-	if *info {
-		lumps, err := w.LoadMapLumps(*mapMarker, "VERTEXES", "LINEDEFS")
-		if err != nil {
-			log.Fatalf("load map lumps: %v", err)
-		}
-		vb := lumps["VERTEXES"]
-		lb := lumps["LINEDEFS"]
-		m, err := mapfmt.LoadMap(lumps)
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		verts := len(vb) / 4
-		lines := len(lb) / 14
-		fmt.Printf("VERTEXES: bytes=%d  count=%d\n", len(vb), verts)
-		fmt.Printf("LINEDEFS: bytes=%d  count=%d\n", len(lb), lines)
-
-		fmt.Printf("Map has %d vertices and %d linedefs\n", len(m.Vertices), len(m.Linedefs))
-		fmt.Printf("First vertex: %+v\n", m.Vertices[0])
-		fmt.Printf("First linedef: %+v\n", m.Linedefs[0])
-
-		if len(vb)%4 != 0 {
-			fmt.Println("WARN: VERTEXES size ist kein Vielfaches von 4 → Format prüfen")
-		}
-		if len(lb)%14 != 0 {
-			fmt.Println("WARN: LINEDEFS size ist kein Vielfaches von 14 → Format prüfen")
-		}
-	}
-
-	// Generiert einzelne Lump Dateien zum Debugen
-	if *extract != "" {
+	var extractLumps []string
+	if strings.TrimSpace(*extract) != "" {
 		want := strings.Split(*extract, ",")
-		for i := range want {
-			want[i] = strings.ToUpper(strings.TrimSpace(want[i]))
-		}
-		lumps, err := w.LoadMapLumps(*mapMarker, want...)
-		if err != nil {
-			log.Fatalf("extract: %v", err)
-		}
-		if err := os.MkdirAll(*outdir, 0o755); err != nil {
-			log.Fatalf("mkdir %s: %v", *outdir, err)
-		}
-		for name, data := range lumps {
-			dst := filepath.Join(*outdir, fmt.Sprintf("%s.lmp", name))
-			if err := os.WriteFile(dst, data, 0o644); err != nil {
-				log.Fatalf("write %s: %v", dst, err)
-			}
-			fmt.Printf("wrote %s (%d bytes)\n", dst, len(data))
-		}
-	}
-
-	// Zum debug test der geo functions
-	if *geomtest {
-		raw, err := w.LoadMapLumps(*mapMarker, "VERTEXES", "LINEDEFS")
-		if err != nil {
-			log.Fatalf("load map lumps: %v", err)
-		}
-		m, err := mapfmt.LoadMap(raw)
-		if err != nil {
-			log.Fatalf("parse map: %v", err)
-		}
-
-		segs := mapfmt.LinedefsToSegs(m.Vertices, m.Linedefs)
-		fmt.Printf("GEOM: vertices=%d linedefs=%d segs=%d\n", len(m.Vertices), len(m.Linedefs), len(segs))
-		if len(segs) == 0 {
-			fmt.Println("GEOM: keine Segmente gefunden – prüfe LINEDEFS/VERTEXES")
-			return
-		}
-
-		pts := make([]geom.Vec, 0, len(m.Vertices))
-		for _, v := range m.Vertices {
-			pts = append(pts, geom.V(float64(v.X), float64(v.Y)))
-		}
-		bb := geom.Bounds(pts)
-		w := bb.Max.X - bb.Min.X
-		h := bb.Max.Y - bb.Min.Y
-		fmt.Printf("AABB: min=(%.1f,%.1f) max=(%.1f,%.1f) size=(%.1f×%.1f)\n",
-			bb.Min.X, bb.Min.Y, bb.Max.X, bb.Max.Y, w, h)
-
-		O := segs[0].A
-		D := geom.Sub(segs[0].B, segs[0].A)
-		if geom.Len(D) < 1e-9 && len(segs) > 1 {
-			O = segs[1].A
-			D = geom.Sub(segs[1].B, segs[1].A)
-		}
-		var left, right, splits, degens int
-		for _, s := range segs {
-			f, b := geom.SplitSeg(s, O, D)
-			if len(f) == 0 && len(b) == 0 {
-				degens++
+		extractLumps = make([]string, 0, len(want))
+		for _, name := range want {
+			n := strings.ToUpper(strings.TrimSpace(name))
+			if n == "" {
 				continue
 			}
-			left += len(f)
-			right += len(b)
-			if len(f) > 0 && len(b) > 0 {
-				splits++
-			}
+			extractLumps = append(extractLumps, n)
 		}
-		fmt.Printf("PROBE-SPLIT: O=(%.1f,%.1f) D=(%.1f,%.1f)\n", O.X, O.Y, D.X, D.Y)
-		fmt.Printf("PROBE-SPLIT: left=%d right=%d splits=%d degens=%d (EPS=%.1e)\n",
-			left, right, splits, degens, geom.EPS)
-
-		return
 	}
 
-	if *buildbsp {
-		raw, err := w.LoadMapLumps(*mapMarker, "VERTEXES", "LINEDEFS")
-		if err != nil {
-			log.Fatalf("load map lumps: %v", err)
-		}
-		m, err := mapfmt.LoadMap(raw)
-		if err != nil {
-			log.Fatalf("parse map: %v", err)
-		}
-
-		segs := mapfmt.LinedefsToSegs(m.Vertices, m.Linedefs)
-		p := bsp.Params{
-			Alpha: *alpha, Beta: *beta, Eps: *eps,
-			MaxDepth: *depth, LeafMax: *leaf, Cands: *cands, Seed: *seed,
-		}
-		root := bsp.Build(segs, p)
-		st := bsp.Measure(root)
-
-		fmt.Printf("BSP built.\n")
-		fmt.Printf("  nodes=%d leaves=%d maxDepth=%d totalLeafSegs=%d\n",
-			st.Nodes, st.Leaves, st.MaxDepth, st.TotalSegs)
-		fmt.Printf("  params: alpha=%.2f beta=%.2f eps=%.1e leafMax=%d maxDepth=%d cands=%d seed=%d\n",
-			p.Alpha, p.Beta, p.Eps, p.LeafMax, p.MaxDepth, p.Cands, p.Seed)
-
-		if *dotOut != "" {
-			if err := viz.EmitDOT(root, *dotOut); err != nil {
-				log.Fatalf("write DOT: %v", err)
-			}
-			fmt.Printf("DOT export geschrieben: %s\n", *dotOut)
-
-			if *treePNG != "" {
-				if err := viz.RunGraphviz(*dotOut, *treePNG); err != nil {
-					log.Printf("Graphviz fehlgeschlagen: %v", err)
-				} else {
-					fmt.Printf("Graphviz PNG gebaut: %s\n", *treePNG)
-				}
-			}
-		}
-
-		if *overlay != "" {
-			if err := viz.RenderPNG(m, root, *overlay); err != nil {
-				log.Fatalf("write overlay PNG: %v", err)
-			}
-			fmt.Printf("Overlay PNG geschrieben: %s\n", *overlay)
-		}
-		return
+	opts := app.Options{
+		WadPath:   *wadPath,
+		MapMarker: *mapMarker,
+		ListOnly:  *listOnly,
+		Info:      *info,
+		Extract:   extractLumps,
+		OutDir:    *outdir,
+		GeomTest:  *geomtest,
+		BuildBSP:  *buildbsp,
+		Alpha:     *alpha,
+		Beta:      *beta,
+		Eps:       *eps,
+		LeafMax:   *leaf,
+		MaxDepth:  *depth,
+		Cands:     *cands,
+		Seed:      *seed,
+		DotOut:    *dotOut,
+		TreePNG:   *treePNG,
+		Overlay:   *overlay,
 	}
 
+	if err := app.Run(opts); err != nil {
+		log.Fatal(err)
+	}
 }