diff --git a/build.gradle.kts b/build.gradle.kts
index d2dfd7e..5c1d24e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -10,7 +10,7 @@ val ktorVersion by extra("2.0.3")
 
 allprojects {
     group = "center.sciprog"
-    version = "0.1.0-dev-3"
+    version = "0.1.0-dev-4"
 }
 
 ksciencePublish{
diff --git a/demo/maps/src/jvmMain/kotlin/Main.kt b/demo/maps/src/jvmMain/kotlin/Main.kt
index fb3debf..989a2c3 100644
--- a/demo/maps/src/jvmMain/kotlin/Main.kt
+++ b/demo/maps/src/jvmMain/kotlin/Main.kt
@@ -24,6 +24,7 @@ import kotlin.math.PI
 import kotlin.random.Random
 import center.sciprog.maps.coordinates.kilometers
 import center.sciprog.maps.coordinates.radians
+import center.sciprog.maps.coordinates.Angle
 
 private fun GeodeticMapCoordinates.toShortString(): String =
     "${(latitude.degrees.value).toString().take(6)}:${(longitude.degrees.value).toString().take(6)}"
@@ -92,7 +93,7 @@ fun App() {
                 drawLine(start = Offset(-10f, 10f), end = Offset(10f, -10f), color = Color.Red)
             }
 
-            arc(pointOne, 10.0.kilometers, 0f.radians, PI.radians)
+            arc(pointOne, 10.0.kilometers, (PI/4).radians, -Angle.pi/2)
 
             line(pointOne, pointTwo, id = "line")
             text(pointOne, "Home", font = { size = 32f })
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 5562473..b4a359b 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
@@ -108,10 +108,14 @@ public class MapLineFeature(
     override fun getBoundingBox(zoom: Double): GmcRectangle = GmcRectangle(a, b)
 }
 
+/**
+ * @param startAngle the angle from parallel downwards for the start of the arc
+ * @param arcLength arc length
+ */
 public class MapArcFeature(
     public val oval: GmcRectangle,
     public val startAngle: Angle,
-    public val endAngle: Angle,
+    public val arcLength: Angle,
     override val zoomRange: IntRange = defaultZoomRange,
     public val color: Color = Color.Red,
 ) : MapFeature {
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 346ba93..433e4f4 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
@@ -134,31 +134,31 @@ public fun MapFeatureBuilder.line(
 public fun MapFeatureBuilder.arc(
     oval: GmcRectangle,
     startAngle: Angle,
-    endAngle: Angle,
+    arcLength: Angle,
     zoomRange: IntRange = defaultZoomRange,
     color: Color = Color.Red,
     id: FeatureId? = null,
 ): FeatureId = addFeature(
     id,
-    MapArcFeature(oval, startAngle, endAngle, zoomRange, color)
+    MapArcFeature(oval, startAngle, arcLength, zoomRange, color)
 )
 
 public fun MapFeatureBuilder.arc(
     center: Pair<Double, Double>,
     radius: Distance,
     startAngle: Angle,
-    endAngle: Angle,
+    arcLength: Angle,
     zoomRange: IntRange = defaultZoomRange,
     color: Color = Color.Red,
     id: FeatureId? = null,
 ): FeatureId = addFeature(
     id,
     MapArcFeature(
-        GmcRectangle.square(center.toCoordinates(), radius, radius),
-        startAngle,
-        endAngle,
-        zoomRange,
-        color
+        oval = GmcRectangle.square(center.toCoordinates(), radius, radius),
+        startAngle = startAngle,
+        arcLength = arcLength,
+        zoomRange = zoomRange,
+        color = color
     )
 )
 
diff --git a/maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapViewJvm.kt b/maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapViewJvm.kt
index 0416684..330a96d 100644
--- a/maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapViewJvm.kt
+++ b/maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapViewJvm.kt
@@ -254,7 +254,7 @@ public actual fun MapView(
                         addArcRad(
                             Rect(topLeft, bottomRight),
                             feature.startAngle.radians.value.toFloat(),
-                            (feature.endAngle - feature.startAngle).radians.value.toFloat()
+                            feature.arcLength.radians.value.toFloat()
                         )
                     }