diff --git a/demo/maps/src/jvmMain/kotlin/Main.kt b/demo/maps/src/jvmMain/kotlin/Main.kt
index 574dc0e..25721ff 100644
--- a/demo/maps/src/jvmMain/kotlin/Main.kt
+++ b/demo/maps/src/jvmMain/kotlin/Main.kt
@@ -5,12 +5,14 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Home
 import androidx.compose.runtime.*
 import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
 import center.sciprog.maps.compose.*
 import center.sciprog.maps.coordinates.Distance
 import center.sciprog.maps.coordinates.GeodeticMapCoordinates
+import center.sciprog.maps.coordinates.GmcBox
 import center.sciprog.maps.coordinates.MapViewPoint
 import io.ktor.client.HttpClient
 import io.ktor.client.engine.cio.CIO
@@ -47,6 +49,27 @@ fun App() {
 
         var centerCoordinates by remember { mutableStateOf<GeodeticMapCoordinates?>(null) }
 
+        val markers = (1..1_000_000).map {
+            val position = GeodeticMapCoordinates.ofDegrees(
+                latitude = Random.nextDouble(-90.0, 90.0),
+                longitude = Random.nextDouble(0.0, 180.0)
+            )
+            MapDrawFeature(
+                position = position,
+                getBoundingBox = {
+                    GmcBox.withCenter(
+                        center = position,
+                        width = Distance(0.001),
+                        height = Distance(0.001)
+                    )
+                }
+            ) {
+                drawRoundRect(
+                    color = Color.Yellow,
+                    size = Size(10f, 10f)
+                )
+            }
+        }
 
         MapView(
             mapTileProvider = mapTileProvider,
@@ -67,11 +90,27 @@ fun App() {
                 centerCoordinates = pointTwo,
             )
 
-            draw(position = pointThree) {
+            draw(
+                position = pointThree,
+                getBoundingBox = {
+                    GmcBox.withCenter(
+                        center = GeodeticMapCoordinates.ofDegrees(
+                            pointThree.first,
+                            pointThree.second
+                        ),
+                        height = Distance(0.001),
+                        width = Distance(0.001)
+                    )
+                }
+            ) {
                 drawLine(start = Offset(-10f, -10f), end = Offset(10f, 10f), color = Color.Red)
                 drawLine(start = Offset(-10f, 10f), end = Offset(10f, -10f), color = Color.Red)
             }
 
+            featureSelector { zoom ->
+                markers.groupBy {  }
+            }
+
             arc(pointOne, Distance(10.0), 0f, PI)
 
             line(pointOne, pointTwo)
diff --git a/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt b/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt
index 2180674..c8fce51 100644
--- a/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt
+++ b/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt
@@ -40,12 +40,10 @@ public class MapFeatureSelector(
 public class MapDrawFeature(
     public val position: GeodeticMapCoordinates,
     override val zoomRange: IntRange = defaultZoomRange,
+    private val getBoundingBox: (zoom: Int) -> GmcBox,
     public val drawFeature: DrawScope.() -> Unit,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox {
-        //TODO add box computation
-        return GmcBox(position, position)
-    }
+    override fun getBoundingBox(zoom: Int): GmcBox = getBoundingBox(zoom)
 }
 
 public class MapCircleFeature(
diff --git a/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt b/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt
index 55f18ee..700acee 100644
--- a/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt
+++ b/maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt
@@ -71,8 +71,9 @@ public fun MapFeatureBuilder.draw(
     position: Pair<Double, Double>,
     zoomRange: IntRange = defaultZoomRange,
     id: FeatureId? = null,
+    getBoundingBox: (Int) -> GmcBox,
     drawFeature: DrawScope.() -> Unit,
-): FeatureId = addFeature(id, MapDrawFeature(position.toCoordinates(), zoomRange, drawFeature))
+): FeatureId = addFeature(id, MapDrawFeature(position.toCoordinates(), zoomRange, getBoundingBox, drawFeature))
 
 public fun MapFeatureBuilder.line(
     aCoordinates: Pair<Double, Double>,
@@ -133,4 +134,14 @@ public fun MapFeatureBuilder.group(
     val map = MapFeatureBuilderImpl(emptyMap()).apply(builder).build()
     val feature = MapFeatureGroup(map, zoomRange)
     return addFeature(id, feature)
-}
\ No newline at end of file
+}
+
+public fun MapFeatureBuilder.featureSelector(
+    id: FeatureId? = null,
+    onSelect: MapFeatureBuilder.(zoom: Int) -> MapFeature
+): FeatureId = addFeature(
+    id = id,
+    feature = MapFeatureSelector(
+        selector = { onSelect(this, it) }
+    )
+)
\ No newline at end of file