diff --git a/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/Trajectory2D.kt b/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/Trajectory2D.kt
index 6aaef55..165d047 100644
--- a/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/Trajectory2D.kt
+++ b/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/Trajectory2D.kt
@@ -71,7 +71,7 @@ public fun StraightTrajectory2D(segment: LineSegment2D): StraightTrajectory2D =
 @Serializable
 @SerialName("arc")
 public data class CircleTrajectory2D(
-    public val circle: Circle2D<Float64>,
+    @Serializable(Circle2DSerializer::class) public val circle: Circle2D<Float64>,
     public val arcStart: Angle,
     public val arcAngle: Angle,
 ) : Trajectory2D {
diff --git a/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/geometryExtensions.kt b/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/geometryExtensions.kt
index b60c24c..50a0ff5 100644
--- a/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/geometryExtensions.kt
+++ b/trajectory-kt/src/commonMain/kotlin/space/kscience/trajectory/geometryExtensions.kt
@@ -1,7 +1,12 @@
 package space.kscience.trajectory
 
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
 import space.kscience.kmath.geometry.*
 import space.kscience.kmath.geometry.euclidean2d.Circle2D
+import space.kscience.kmath.geometry.euclidean2d.Float64Circle2D
 import space.kscience.kmath.geometry.euclidean2d.Float64Space2D
 import space.kscience.kmath.structures.Float64
 import kotlin.math.abs
@@ -95,3 +100,21 @@ public fun CircleTrajectory2D.containsPoint(point: Vector2D<Float64>): Boolean =
         else -> arcAngle < offset - Angle.piTimes2
     }
 }
+
+internal object Circle2DSerializer : KSerializer<Circle2D<Float64>> {
+    private val serializer = Float64Circle2D.serializer()
+
+    override val descriptor: SerialDescriptor
+        get() = serializer.descriptor
+
+    override fun deserialize(decoder: Decoder): Circle2D<Float64> {
+        return decoder.decodeSerializableValue(serializer)
+    }
+
+    override fun serialize(encoder: Encoder, value: Circle2D<Float64>) {
+        encoder.encodeSerializableValue(
+            serializer,
+            value as? Float64Circle2D ?: Float64Circle2D(value.center, value.radius)
+        )
+    }
+}
\ No newline at end of file
diff --git a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/ArcTests.kt b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/ArcTests.kt
similarity index 89%
rename from trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/ArcTests.kt
rename to trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/ArcTests.kt
index dbc273c..b3a3da7 100644
--- a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/ArcTests.kt
+++ b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/ArcTests.kt
@@ -3,15 +3,13 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package space.kscience.kmath.geometry
+package space.kscience.trajectory
 
+import space.kscience.kmath.geometry.Angle
 import space.kscience.kmath.geometry.euclidean2d.Circle2D
 import space.kscience.kmath.geometry.euclidean2d.Float64Space2D
 import space.kscience.kmath.geometry.euclidean2d.circumference
-import space.kscience.trajectory.CircleTrajectory2D
-import space.kscience.trajectory.Trajectory2D
-import space.kscience.trajectory.circle
-import space.kscience.trajectory.containsPoint
+import space.kscience.kmath.geometry.radians
 import kotlin.math.PI
 import kotlin.test.Test
 import kotlin.test.assertEquals
diff --git a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/CircleTests.kt b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/CircleTests.kt
similarity index 95%
rename from trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/CircleTests.kt
rename to trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/CircleTests.kt
index aae26d5..cb35191 100644
--- a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/CircleTests.kt
+++ b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/CircleTests.kt
@@ -3,16 +3,13 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package space.kscience.kmath.geometry
+package space.kscience.trajectory
 
+import space.kscience.kmath.geometry.LineSegment2D
 import space.kscience.kmath.geometry.euclidean2d.Circle2D
 import space.kscience.kmath.geometry.euclidean2d.Float64Space2D
 import space.kscience.kmath.geometry.euclidean2d.circumference
 import space.kscience.kmath.structures.Float64
-import space.kscience.trajectory.circle
-import space.kscience.trajectory.intersects
-import space.kscience.trajectory.intersectsOrInside
-import space.kscience.trajectory.segment
 import kotlin.math.pow
 import kotlin.math.sqrt
 import kotlin.test.Test
diff --git a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/LineTests.kt b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/LineTests.kt
similarity index 93%
rename from trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/LineTests.kt
rename to trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/LineTests.kt
index eaea514..d304289 100644
--- a/trajectory-kt/src/commonTest/kotlin/space/kscience/kmath/geometry/LineTests.kt
+++ b/trajectory-kt/src/commonTest/kotlin/space/kscience/trajectory/LineTests.kt
@@ -3,10 +3,9 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package space.kscience.kmath.geometry
+package space.kscience.trajectory
 
 import space.kscience.kmath.geometry.euclidean2d.Float64Space2D
-import space.kscience.trajectory.StraightTrajectory2D
 import kotlin.math.pow
 import kotlin.math.sqrt
 import kotlin.test.Test