diff --git a/src/CircleTool.cpp b/src/CircleTool.cpp
index a1dc726..2383974 100644
--- a/src/CircleTool.cpp
+++ b/src/CircleTool.cpp
@@ -15,6 +15,10 @@
 #include <QOpenGLShaderProgram>
 #include <cmath>
 #include <QtMath>
+#include <optional>
+#include <gp_Ax2.hxx>
+#include <gp_Pnt2d.hxx>
+#include <ElCLib.hxx>
 
 CircleTool::CircleTool(ViewportWidget* viewport)
     : SketchTool(viewport)
@@ -35,14 +39,18 @@ void CircleTool::activate()
 
 void CircleTool::mousePressEvent(QMouseEvent *event)
 {
+    auto currentPlaneOpt = m_viewport->currentPlane();
+    if (!currentPlaneOpt) return;
+    const auto& plane = currentPlaneOpt.value();
+
     gp_Pnt p;
     if (!m_isDefining) {
         if (m_viewport->isSnappingOrigin()) {
-            p.SetCoord(0, 0, 0);
+            p = plane.Location();
         } else if (m_viewport->isSnappingVertex()) {
             p = m_viewport->snapVertex();
         } else {
-            QVector3D worldPos = m_viewport->unproject(event->pos(), m_viewport->currentPlane());
+            QVector3D worldPos = m_viewport->unproject(event->pos(), plane);
             p.SetCoord(worldPos.x(), worldPos.y(), worldPos.z());
         }
         m_centerPoint = p;
@@ -70,24 +78,22 @@ void CircleTool::mousePressEvent(QMouseEvent *event)
         }
 
         if (diameterFromInput) {
-            QVector3D mousePos = m_viewport->unproject(event->pos(), m_viewport->currentPlane());
+            QVector3D mousePos = m_viewport->unproject(event->pos(), plane);
             QVector3D mouseDir = mousePos - centerPos;
             if (mouseDir.lengthSquared() < 1e-9) {
-                if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY || m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
-                    mouseDir = QVector3D(1, 0, 0);
-                } else { // YZ
-                    mouseDir = QVector3D(0, 1, 0);
-                }
+                const auto& xDir = plane.XDirection();
+                mouseDir = QVector3D(xDir.X(), xDir.Y(), xDir.Z());
             }
             double radius = inputDiameter / 2.0;
             worldPos = centerPos + mouseDir.normalized() * radius;
         } else {
             if (m_viewport->isSnappingOrigin()) {
-                worldPos.setX(0); worldPos.setY(0); worldPos.setZ(0);
+                const auto& origin = plane.Location();
+                worldPos.setX(origin.X()); worldPos.setY(origin.Y()); worldPos.setZ(origin.Z());
             } else if (m_viewport->isSnappingVertex()) {
                 worldPos = QVector3D(m_viewport->snapVertex().X(), m_viewport->snapVertex().Y(), m_viewport->snapVertex().Z());
             } else {
-                worldPos = m_viewport->unproject(event->pos(), m_viewport->currentPlane());
+                worldPos = m_viewport->unproject(event->pos(), plane);
             }
         }
         p.SetCoord(worldPos.x(), worldPos.y(), worldPos.z());
@@ -103,6 +109,10 @@ void CircleTool::mouseMoveEvent(QMouseEvent *event)
 
 void CircleTool::finalizeCreation()
 {
+    auto currentPlaneOpt = m_viewport->currentPlane();
+    if (!currentPlaneOpt) return;
+    const auto& plane = currentPlaneOpt.value();
+
     QVector3D worldPos;
     QVector3D centerPos(m_centerPoint.X(), m_centerPoint.Y(), m_centerPoint.Z());
 
@@ -117,19 +127,16 @@ void CircleTool::finalizeCreation()
     }
 
     if (diameterFromInput) {
-        QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), m_viewport->currentPlane());
+        QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), plane);
         QVector3D mouseDir = mousePos - centerPos;
         if (mouseDir.lengthSquared() < 1e-9) {
-            if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY || m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
-                mouseDir = QVector3D(1, 0, 0);
-            } else { // YZ
-                mouseDir = QVector3D(0, 1, 0);
-            }
+            const auto& xDir = plane.XDirection();
+            mouseDir = QVector3D(xDir.X(), xDir.Y(), xDir.Z());
         }
         double radius = inputDiameter / 2.0;
         worldPos = centerPos + mouseDir.normalized() * radius;
     } else {
-        worldPos = m_viewport->unproject(m_viewport->currentMousePos(), m_viewport->currentPlane());
+        worldPos = m_viewport->unproject(m_viewport->currentMousePos(), plane);
     }
 
     gp_Pnt p;
@@ -141,134 +148,121 @@ void CircleTool::finalizeCreation()
 
 void CircleTool::paintGL()
 {
-    if (m_isDefining) {
-        QVector<GLfloat> vertices;
-        QVector3D worldPos;
-        QVector3D centerPos(m_centerPoint.X(), m_centerPoint.Y(), m_centerPoint.Z());
+    auto currentPlaneOpt = m_viewport->currentPlane();
+    if (!m_isDefining || !currentPlaneOpt) return;
+    const auto& plane = currentPlaneOpt.value();
 
-        QString diameterInput = m_viewport->property("diameterInput").toString();
-        bool diameterFromInput = false;
-        double inputDiameter = 0;
+    QVector<GLfloat> vertices;
+    QVector3D worldPos;
+    QVector3D centerPos(m_centerPoint.X(), m_centerPoint.Y(), m_centerPoint.Z());
 
-        if (!diameterInput.isEmpty()) {
-            bool ok;
-            inputDiameter = diameterInput.toDouble(&ok);
-            if (ok) diameterFromInput = true;
-        }
+    QString diameterInput = m_viewport->property("diameterInput").toString();
+    bool diameterFromInput = false;
+    double inputDiameter = 0;
 
-        QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), m_viewport->currentPlane());
-
-        double radius;
-        if (diameterFromInput) {
-            radius = inputDiameter / 2.0;
-        } else {
-            worldPos = mousePos;
-            if (m_viewport->isSnappingOrigin()) {
-                worldPos.setX(0); worldPos.setY(0); worldPos.setZ(0);
-            } else if (m_viewport->isSnappingVertex()) {
-                worldPos.setX(m_viewport->snapVertex().X()); worldPos.setY(m_viewport->snapVertex().Y()); worldPos.setZ(m_viewport->snapVertex().Z());
-            }
-            radius = (worldPos - centerPos).length();
-        }
-
-        const int segments = 64;
-        for (int i = 0; i < segments; ++i) {
-            double angle1 = i * 2.0 * M_PI / segments;
-            double angle2 = (i + 1) * 2.0 * M_PI / segments;
-
-            QVector3D p1, p2;
-
-            if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY) {
-                p1.setX(centerPos.x() + radius * qCos(angle1));
-                p1.setY(centerPos.y() + radius * qSin(angle1));
-                p1.setZ(centerPos.z());
-                p2.setX(centerPos.x() + radius * qCos(angle2));
-                p2.setY(centerPos.y() + radius * qSin(angle2));
-                p2.setZ(centerPos.z());
-            } else if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
-                p1.setX(centerPos.x() + radius * qCos(angle1));
-                p1.setY(centerPos.y());
-                p1.setZ(centerPos.z() + radius * qSin(angle1));
-                p2.setX(centerPos.x() + radius * qCos(angle2));
-                p2.setY(centerPos.y());
-                p2.setZ(centerPos.z() + radius * qSin(angle2));
-            } else { // YZ
-                p1.setX(centerPos.x());
-                p1.setY(centerPos.y() + radius * qCos(angle1));
-                p1.setZ(centerPos.z() + radius * qSin(angle1));
-                p2.setX(centerPos.x());
-                p2.setY(centerPos.y() + radius * qCos(angle2));
-                p2.setZ(centerPos.z() + radius * qSin(angle2));
-            }
-            vertices << p1.x() << p1.y() << p1.z();
-            vertices << p2.x() << p2.y() << p2.z();
-        }
-
-        m_viewport->shaderProgram()->setUniformValue(m_viewport->colorLoc(), QVector4D(1.0f, 1.0f, 0.0f, 1.0f));
-        m_viewport->vbo().bind();
-        m_viewport->vbo().allocate(vertices.constData(), vertices.size() * sizeof(GLfloat));
-        glDrawArrays(GL_LINES, 0, segments * 2);
+    if (!diameterInput.isEmpty()) {
+        bool ok;
+        inputDiameter = diameterInput.toDouble(&ok);
+        if (ok) diameterFromInput = true;
     }
+
+    QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), plane);
+
+    double radius;
+    if (diameterFromInput) {
+        radius = inputDiameter / 2.0;
+    } else {
+        worldPos = mousePos;
+        if (m_viewport->isSnappingOrigin()) {
+            const auto& origin = plane.Location();
+            worldPos.setX(origin.X()); worldPos.setY(origin.Y()); worldPos.setZ(origin.Z());
+        } else if (m_viewport->isSnappingVertex()) {
+            worldPos.setX(m_viewport->snapVertex().X()); worldPos.setY(m_viewport->snapVertex().Y()); worldPos.setZ(m_viewport->snapVertex().Z());
+        }
+        radius = (worldPos - centerPos).length();
+    }
+
+    const int segments = 64;
+    const auto& xDir = plane.XDirection();
+    const auto& yDir = plane.YDirection();
+    QVector3D u_axis(xDir.X(), xDir.Y(), xDir.Z());
+    QVector3D v_axis(yDir.X(), yDir.Y(), yDir.Z());
+
+    for (int i = 0; i < segments; ++i) {
+        double angle1 = i * 2.0 * M_PI / segments;
+        double angle2 = (i + 1) * 2.0 * M_PI / segments;
+
+        QVector3D p1 = centerPos + radius * (qCos(angle1) * u_axis + qSin(angle1) * v_axis);
+        QVector3D p2 = centerPos + radius * (qCos(angle2) * u_axis + qSin(angle2) * v_axis);
+
+        vertices << p1.x() << p1.y() << p1.z();
+        vertices << p2.x() << p2.y() << p2.z();
+    }
+
+    m_viewport->shaderProgram()->setUniformValue(m_viewport->colorLoc(), QVector4D(1.0f, 1.0f, 0.0f, 1.0f));
+    m_viewport->vbo().bind();
+    m_viewport->vbo().allocate(vertices.constData(), vertices.size() * sizeof(GLfloat));
+    glDrawArrays(GL_LINES, 0, segments * 2);
 }
 
 void CircleTool::paint2D(QPainter& painter, const QMatrix4x4& modelView, const QMatrix4x4& projection)
 {
-    if (m_isDefining) {
-        QVector3D worldPos;
-        QVector3D centerPos(m_centerPoint.X(), m_centerPoint.Y(), m_centerPoint.Z());
+    auto currentPlaneOpt = m_viewport->currentPlane();
+    if (!m_isDefining || !currentPlaneOpt) return;
+    const auto& plane = currentPlaneOpt.value();
 
-        QString diameterInput = m_viewport->property("diameterInput").toString();
-        bool diameterFromInput = false;
-        double inputDiameter = 0;
+    QVector3D worldPos;
+    QVector3D centerPos(m_centerPoint.X(), m_centerPoint.Y(), m_centerPoint.Z());
 
-        if (!diameterInput.isEmpty()) {
-            bool ok;
-            inputDiameter = diameterInput.toDouble(&ok);
-            if (ok) diameterFromInput = true;
+    QString diameterInput = m_viewport->property("diameterInput").toString();
+    bool diameterFromInput = false;
+    double inputDiameter = 0;
+
+    if (!diameterInput.isEmpty()) {
+        bool ok;
+        inputDiameter = diameterInput.toDouble(&ok);
+        if (ok) diameterFromInput = true;
+    }
+
+    QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), plane);
+    QVector3D edgePos;
+    double diameter;
+
+    if (diameterFromInput) {
+        diameter = inputDiameter;
+        QVector3D mouseDir = mousePos - centerPos;
+        if (mouseDir.lengthSquared() < 1e-9) {
+            const auto& xDir = plane.XDirection();
+            mouseDir = QVector3D(xDir.X(), xDir.Y(), xDir.Z());
         }
+        edgePos = centerPos + mouseDir.normalized() * (diameter / 2.0);
+    } else {
+        edgePos = mousePos;
+        if (m_viewport->isSnappingOrigin()) {
+            const auto& origin = plane.Location();
+            edgePos.setX(origin.X()); edgePos.setY(origin.Y()); edgePos.setZ(origin.Z());
+        } else if (m_viewport->isSnappingVertex()) {
+            edgePos.setX(m_viewport->snapVertex().X()); edgePos.setY(m_viewport->snapVertex().Y()); edgePos.setZ(m_viewport->snapVertex().Z());
+        }
+        diameter = (edgePos - centerPos).length() * 2.0;
+    }
 
-        QVector3D mousePos = m_viewport->unproject(m_viewport->currentMousePos(), m_viewport->currentPlane());
-        QVector3D edgePos;
-        double diameter;
+    painter.setRenderHint(QPainter::Antialiasing);
+    QFontMetrics fm(painter.font());
 
-        if (diameterFromInput) {
-            diameter = inputDiameter;
-            QVector3D mouseDir = mousePos - centerPos;
-            if (mouseDir.lengthSquared() < 1e-9) {
-                if (m_viewport->currentPlane() == ViewportWidget::SketchPlane::XY || m_viewport->currentPlane() == ViewportWidget::SketchPlane::XZ) {
-                    mouseDir = QVector3D(1, 0, 0);
-                } else { // YZ
-                    mouseDir = QVector3D(0, 1, 0);
-                }
-            }
-            edgePos = centerPos + mouseDir.normalized() * (diameter / 2.0);
+    // Diameter dimension
+    QVector3D diameterTextPos3D = (centerPos + edgePos) / 2.0f;
+    QVector3D screenPosD = m_viewport->project(diameterTextPos3D, modelView, projection, m_viewport->rect());
+    if (screenPosD.z() < 1.0f) {
+        QString diameterText = diameterFromInput ? diameterInput : QString::number(diameter, 'f', 2);
+        QRect textRect = fm.boundingRect(diameterText + "__");
+        textRect.moveCenter(screenPosD.toPoint());
+        if (m_viewport->property("dimensionEditMode").toString() == "diameter") {
+            painter.fillRect(textRect.adjusted(-4, -2, 4, 2), QColor(64, 128, 255));
         } else {
-            edgePos = mousePos;
-            if (m_viewport->isSnappingOrigin()) {
-                edgePos.setX(0); edgePos.setY(0); edgePos.setZ(0);
-            } else if (m_viewport->isSnappingVertex()) {
-                edgePos.setX(m_viewport->snapVertex().X()); edgePos.setY(m_viewport->snapVertex().Y()); edgePos.setZ(m_viewport->snapVertex().Z());
-            }
-            diameter = (edgePos - centerPos).length() * 2.0;
-        }
-
-        painter.setRenderHint(QPainter::Antialiasing);
-        QFontMetrics fm(painter.font());
-
-        // Diameter dimension
-        QVector3D diameterTextPos3D = (centerPos + edgePos) / 2.0f;
-        QVector3D screenPosD = m_viewport->project(diameterTextPos3D, modelView, projection, m_viewport->rect());
-        if (screenPosD.z() < 1.0f) {
-            QString diameterText = diameterFromInput ? diameterInput : QString::number(diameter, 'f', 2);
-            QRect textRect = fm.boundingRect(diameterText + "__");
-            textRect.moveCenter(screenPosD.toPoint());
-            if (m_viewport->property("dimensionEditMode").toString() == "diameter") {
-                painter.fillRect(textRect.adjusted(-4, -2, 4, 2), QColor(64, 128, 255));
-            } else {
-                painter.fillRect(textRect.adjusted(-4, -2, 4, 2), QColor(50, 50, 50));
-            }
-            painter.setPen(Qt::white);
-            painter.drawText(textRect, Qt::AlignCenter, diameterText);
+            painter.fillRect(textRect.adjusted(-4, -2, 4, 2), QColor(50, 50, 50));
         }
+        painter.setPen(Qt::white);
+        painter.drawText(textRect, Qt::AlignCenter, diameterText);
     }
 }