diff --git a/web/app/math/math.js b/web/app/math/math.js
index 96e5beb3..e1786dcf 100644
--- a/web/app/math/math.js
+++ b/web/app/math/math.js
@@ -230,10 +230,12 @@ export function findLowestLeftPoint(poly) {
   return heroIdx;
 }
 
+const _360 = 2 * Math.PI;
+
 export function makeAngle0_360(angle) {
-  angle %= 2 * Math.PI;
+  angle %= _360;
   if (angle < 0) {
-    angle = 2 * Math.PI + angle;
+    angle = _360 + angle;
   }
   return angle;
 } 
diff --git a/web/app/sketcher/actions/constraintActions.js b/web/app/sketcher/actions/constraintActions.js
index 92012102..d9b5622e 100644
--- a/web/app/sketcher/actions/constraintActions.js
+++ b/web/app/sketcher/actions/constraintActions.js
@@ -5,6 +5,7 @@ import {Segment} from "../shapes/segment";
 import {isInstanceOf, matchAll, matchTypes, sortSelectionByType} from "./matchUtils";
 import constraints from "../../../test/cases/constraints";
 import {Arc} from "../shapes/arc";
+import {FilletTool} from "../tools/fillet";
 
 export default [
 
@@ -48,6 +49,31 @@ export default [
 
   },
 
+  {
+    shortName: 'EqualRadius',
+    description: 'Equal Radius Between Two Circle',
+    selectionMatcher: selection => {
+      for (let obj of selection) {
+        if (!(isInstanceOf(obj, Circle) || isInstanceOf(obj, Arc))) {
+          return false;
+        }
+      }
+      return true;
+    },
+
+    invoke: ctx => {
+
+      const {viewer} = ctx;
+
+      const pm = viewer.parametricManager;
+      for (let i = 1; i < viewer.selected.length; ++i) {
+        pm._add(new AlgNumConstraint(ConstraintDefinitions.EqualRadius, [viewer.selected[i-1], viewer.selected[i]]));
+      }
+      pm.commit();
+    }
+
+  },
+
   {
     shortName: 'Point On Line',
     description: 'Point On Line',
@@ -155,20 +181,34 @@ export default [
     description: 'Add a Fillet',
     selectionMatcher: (selection) => {
       if (matchTypes(selection, EndPoint, 1)) {
-
-      } else {
-        return false;
+        const [point] = selection;
+        if (isInstanceOf(point.parent, Segment)) {
+          let pair = null;
+          point.visitLinked(l => {
+            if (l !== point && isInstanceOf(l.parent, Segment)) {
+              pair = l;
+              return true;
+            }
+          });
+          if (pair) {
+            return true;
+          }
+        }
       }
+      return false;
     },
 
     invoke: ctx => {
       const {viewer} = ctx;
 
-      const [point] = viewer.selected;
 
-      const constr = new AlgNumConstraint(ConstraintDefinitions.LockPoint, [point]);
-      constr.initConstants();
-      editConstraint(ctx, constr, () => viewer.parametricManager.add(constr));
+
+      const filletTool = new FilletTool(ctx.viewer);
+      const cands = filletTool.getCandidateFromSelection(viewer.selected);
+      if (cands) {
+        filletTool.breakLinkAndMakeFillet(cands[0], cands[1]);
+      }
+
     }
   },
 
diff --git a/web/app/sketcher/actions/matchUtils.js b/web/app/sketcher/actions/matchUtils.js
index 7cd8d0f4..d1ffd1fe 100644
--- a/web/app/sketcher/actions/matchUtils.js
+++ b/web/app/sketcher/actions/matchUtils.js
@@ -34,6 +34,9 @@ export function matchTypes(selection) {
 }
 
 export function isInstanceOf(obj, shapeConstructor) {
+  if (!obj) {
+    return false;
+  }
   return obj._class === shapeConstructor.prototype._class;
 }
 
diff --git a/web/app/sketcher/constr/ANConstraints.js b/web/app/sketcher/constr/ANConstraints.js
index d1aec98d..9e92b09e 100644
--- a/web/app/sketcher/constr/ANConstraints.js
+++ b/web/app/sketcher/constr/ANConstraints.js
@@ -239,6 +239,19 @@ export const ConstraintDefinitions = {
     },
   },
 
+  EqualRadius: {
+    id: 'EqualRadius',
+    name: 'Equal Radius',
+
+    defineParamsScope: ([c1, c2], callback) => {
+      callback(c1.r);
+      callback(c2.r);
+    },
+
+    collectPolynomials: (polynomials, [r1, r2]) => {
+      polynomials.push(new Polynomial().monomial().term(r1, POW_1_FN).monomial(-1).term(r2, POW_1_FN).monomial(1));
+    },
+  },
 
   LockPoint: {
     id: 'LockPoint',
@@ -307,14 +320,17 @@ export const ConstraintDefinitions = {
     },
 
     defineParamsScope: ([l1, l2, arc], callback) => {
-      l1.collectParams(callback);
-      l2.collectParams(callback);
-      arc.collectParams(callback);
+      callback(l1.params.ang);
+      callback(l1.params.w);
+      callback(l2.params.ang);
+      callback(l2.params.w);
+      arc.c.visitParams(callback);
+      callback(arc.r);
     },
 
-    collectPolynomials: (polynomials, [ang1, w1, cx1, cy1, r1, ang2, w2, cx2, cy2, r2], {inverted1, inverted2}) => {
-      polynomials.push(tangentLCPolynomial(ang1, w1, cx1, cy1, r1, inverted1));
-      polynomials.push(tangentLCPolynomial(ang2, w2, cx2, cy2, r2, inverted2));
+    collectPolynomials: (polynomials, [ang1, w1, ang2, w2, cx, cy, r], {inverted1, inverted2}) => {
+      polynomials.push(tangentLCPolynomial(ang1, w1, cx, cy, r, inverted1));
+      polynomials.push(tangentLCPolynomial(ang2, w2, cx, cy, r, inverted2));
     },
 
   },
@@ -411,13 +427,14 @@ export class AlgNumConstraint {
       }
       Object.keys(this.constants).map(name => {
         let def = this.schema.constants[name];
+        let val = this.constants[name];
         if (def.type === 'number') {
-          let val = parseFloat(this.constants[name]);
-          if (def.transform) {
-            val = def.transform(val);
-          }
-          this.resolvedConstants[name] = val;
+          val = parseFloat(val);
         }
+        if (def.transform) {
+          val = def.transform(val);
+        }
+        this.resolvedConstants[name] = val;
       });
     }
   }
diff --git a/web/app/sketcher/constr/AlgNumSystem.js b/web/app/sketcher/constr/AlgNumSystem.js
index 79973657..b4a7c31b 100644
--- a/web/app/sketcher/constr/AlgNumSystem.js
+++ b/web/app/sketcher/constr/AlgNumSystem.js
@@ -3,6 +3,8 @@ import {eqEps} from "../../brep/geom/tolerance";
 import {Polynomial, POW_1_FN} from "./polynomial";
 import {compositeFn} from "gems/func";
 
+const DEBUG = true;
+
 export class AlgNumSubSystem {
 
   modifiers = [];
@@ -54,7 +56,6 @@ export class AlgNumSubSystem {
     this.prepare();
     if (!this.isConflicting(constraint)) {
       this.solveFine();
-      console.log(this.solveStatus);
       if (!this.solveStatus.success) {
         console.log("adding to conflicts");
         this.conflicting.add(constraint);
@@ -121,9 +122,10 @@ export class AlgNumSubSystem {
       c.collectPolynomials(this.polynomials);
       this.polynomials.forEach(p => this.polyToConstr.set(p, c))
     });
-
-    console.log('reducing system:');
-    this.polynomials.forEach(p => console.log(p.toString()));
+    if (DEBUG) {
+      console.log('reducing system:');
+      this.polynomials.forEach(p => console.log(p.toString()));
+    }
 
     let requirePass = true;
 
@@ -137,10 +139,12 @@ export class AlgNumSubSystem {
 
         if (polynomial.monomials.length === 0) {
           this.conflicting.add(this.polyToConstr.get(polynomial));
-          console.log("CONFLICT: " + polynomial.toString());
+          if (DEBUG) {
+            console.log("CONFLICT: " + polynomial.toString());
+          }
           if (eqEps(polynomial.constant, 0)) {
             this.redundant.add(this.polyToConstr.get(polynomial));
-            console.log("REDUNDANT");
+            // console.log("REDUNDANT");
           }
           this.polynomials[i] = null;
         } else if (polynomial.isLinear && polynomial.monomials.length === 1) {
@@ -236,14 +240,16 @@ export class AlgNumSubSystem {
       iso.beingSolvedParams.forEach(solverParam => this.paramToIsolation.set(solverParam.objectParam, iso))
     });
 
-    console.log('solving system:');
-    this.polynomialIsolations.forEach((iso, i) => {
-      console.log(i + ". ISOLATION, DOF: " + iso.dof);
-      iso.polynomials.forEach(p => console.log(p.toString()));
-    });
+    if (DEBUG) {
+      console.log('solving system:');
+      this.polynomialIsolations.forEach((iso, i) => {
+        console.log(i + ". ISOLATION, DOF: " + iso.dof);
+        iso.polynomials.forEach(p => console.log(p.toString()));
+      });
 
-    console.log('with respect to:');
-    this.substitutionOrder.forEach(x => console.log('X' + x.id  + ' = ' + this.substitutedParams.get(x).toString()));
+      console.log('with respect to:');
+      this.substitutionOrder.forEach(x => console.log('X' + x.id + ' = ' + this.substitutedParams.get(x).toString()));
+    }
   }
 
   splitByIsolatedClusters(polynomials) {
@@ -337,7 +343,9 @@ export class AlgNumSubSystem {
         this.solveStatus.success = this.solveStatus.success && iso.solveStatus.success;
       });
 
-      console.log('numerical result: ' + this.solveStatus.success);
+      if (DEBUG) {
+        console.log('numerical result: ' + this.solveStatus.success);
+      }
     }
 
     for (let [p, val] of this.eliminatedParams) {
@@ -422,7 +430,7 @@ class Isolation {
     });
 
     if (penaltyFunction.params.length) {
-      residuals.push(penaltyFunction);
+      // residuals.push(penaltyFunction);
     }
 
     this.numericalSolver = prepare(residuals);
diff --git a/web/app/sketcher/history.js b/web/app/sketcher/history.js
index 8572b83e..a196e66e 100644
--- a/web/app/sketcher/history.js
+++ b/web/app/sketcher/history.js
@@ -43,7 +43,7 @@ HistoryManager.prototype.lightCheckpoint = function (weight) {
 
 HistoryManager.prototype.checkpoint = function () {
   try {
-    this._checkpoint();
+    // this._checkpoint();
   } catch(e) {
     console.log(e);
   }
diff --git a/web/app/sketcher/shapes/arc.js b/web/app/sketcher/shapes/arc.js
index 0c579311..40751e16 100644
--- a/web/app/sketcher/shapes/arc.js
+++ b/web/app/sketcher/shapes/arc.js
@@ -5,6 +5,7 @@ import {Param} from "./param";
 import {greaterThanConstraint} from "../constr/barriers";
 import {MIN_RADIUS} from "./circle";
 import {AlgNumConstraint, ConstraintDefinitions} from "../constr/ANConstraints";
+import {makeAngle0_360} from "../../math/math";
 
 export class Arc extends SketchObject {
   
@@ -20,7 +21,6 @@ export class Arc extends SketchObject {
 
     this.r = new Param(MIN_RADIUS + 0.001);
     this.r.constraints = [greaterThanConstraint(MIN_RADIUS)];
-
     this.ang1 = new Param(0);
     this.ang2 = new Param(0);
 
@@ -84,13 +84,13 @@ export class Arc extends SketchObject {
   drawImpl(ctx, scale) {
     ctx.beginPath();
     let r = this.radiusForDrawing();
-    let startAngle = this.getStartAngle();
+    let startAngle = makeAngle0_360(this.getStartAngle());
     let endAngle;
     if (math.areEqual(this.a.x, this.b.x, math.TOLERANCE) &&
         math.areEqual(this.a.y, this.b.y, math.TOLERANCE)) {
       endAngle = startAngle + 2 * Math.PI;
     } else {
-      endAngle = this.getEndAngle();
+      endAngle = makeAngle0_360(this.getEndAngle());
     }
     ctx.arc(this.c.x, this.c.y, r, startAngle, endAngle);
     let distanceB = this.distanceB();
diff --git a/web/app/sketcher/tools/circle.js b/web/app/sketcher/tools/circle.js
index a6b4f80f..1ab5cb5c 100644
--- a/web/app/sketcher/tools/circle.js
+++ b/web/app/sketcher/tools/circle.js
@@ -51,7 +51,7 @@ export class EditCircleTool extends Tool {
     this.circle = new Circle(
       new EndPoint(p.x, p.y)
     );
-    if (needSnap) this.viewer.parametricManager.linkObjects([this.circle.c, p]);
+    if (needSnap) this.viewer.parametricManager.coincidePoints(this.circle.c, p);
     this.pointPicked(this.circle.c.x, this.circle.c.y);
     this.sendHint('specify radius');
     this.viewer.activeLayer.add(this.circle);
diff --git a/web/app/sketcher/tools/fillet.js b/web/app/sketcher/tools/fillet.js
index f4f8d355..cec74c52 100644
--- a/web/app/sketcher/tools/fillet.js
+++ b/web/app/sketcher/tools/fillet.js
@@ -6,6 +6,9 @@ import {EndPoint} from '../shapes/point'
 import {Arc} from '../shapes/arc'
 import {Constraints} from '../parametric'
 import {Tool} from './tool'
+import {isInstanceOf} from "../actions/matchUtils";
+import {Segment} from "../shapes/segment";
+import {AlgNumConstraint, ConstraintDefinitions} from "../constr/ANConstraints";
 
 export class FilletTool extends Tool {
   
@@ -15,22 +18,18 @@ export class FilletTool extends Tool {
   }
   
   restart() {
-    for (let master of this.viewer.selected) {
-      if (master instanceof EndPoint) {
-        for (let slave of master.linked) {
-          if (slave instanceof EndPoint) {
-            if (this.breakLinkAndMakeFillet(master, slave)) {
-              this.viewer.toolManager.releaseControl();
-            }
-          }
-        }        
+    const cands = this.getCandidateFromSelection(this.viewer.selected);
+    if (cands) {
+      const [c1, c2] = cands;
+      if (this.breakLinkAndMakeFillet(c1, c2)) {
+        this.viewer.toolManager.releaseControl();
       }
     }
   }
   
   makeFillet(point1, point2) {
     function shrink(point1) {
-      var a, b;
+      let a, b;
       if (point1.id === point1.parent.a.id) {
         a = point1.parent.b;
         b = point1.parent.a;
@@ -38,37 +37,50 @@ export class FilletTool extends Tool {
         a = point1.parent.a;
         b = point1.parent.b;
       }
-      var d = math.distanceAB(a, b);
-      var k = 4 / 5;
+      const d = math.distanceAB(a, b);
+      const k = 4 / 5;
       b.x = a.x + (b.x - a.x) * k;
       b.y = a.y + (b.y - a.y) * k;
       return new Vector(a.x - b.x, a.y - b.y, 0);
     }
-  
-    var v1 = shrink(point1);
-    var v2 = shrink(point2);
+
+    const v1 = shrink(point1);
+    const v2 = shrink(point2);
   
     if (v1.cross(v2).z > 0) {
-      var _ = point1;
+      const _ = point1;
       point1 = point2;
       point2 = _;
     }
-  
-    var vec = new Vector();
+
+    const vec = new Vector();
     vec.setV(point2);
     vec._minus(point1);
     vec._multiply(0.5);
     vec._plus(point1);
   
-    var arc = new Arc(
+    const arc = new Arc(
       new EndPoint(point1.x, point1.y),
       new EndPoint(point2.x, point2.y),
       new EndPoint(vec.x, vec.y));
     point1.parent.layer.add(arc);
-    var pm = this.viewer.parametricManager;
+    const pm = this.viewer.parametricManager;
+
+    const s1 = point1.parent;
+    const s2 = point2.parent;
+
+    const inverted1 = Math.cos(s1.ang) * arc.c.x + Math.sin(s1.ang) * arc.c.y < s1.w;
+    const inverted2 = Math.cos(s2.ang) * arc.c.x + Math.sin(s2.ang) * arc.c.y < s2.w;
     arc.stabilize(this.viewer);
-    pm._add(new Constraints.Fillet( point1, point2, arc));
-    
+
+    pm.add(new AlgNumConstraint(ConstraintDefinitions.Fillet, [point1.parent, point2.parent, arc], {
+      inverted1,
+      inverted2
+    }));
+
+    pm.add(new AlgNumConstraint(ConstraintDefinitions.PCoincident, [point1, arc.a]));
+    pm.add(new AlgNumConstraint(ConstraintDefinitions.PCoincident, [point2, arc.b]));
+
     //function otherEnd(point) {
     //  if (point.parent.a.id === point.id) {
     //    return point.parent.b;
@@ -80,10 +92,10 @@ export class FilletTool extends Tool {
     //pm._add(new Constraints.LockConvex(arc.c, arc.a, otherEnd(point1)));
     //pm._add(new Constraints.LockConvex(otherEnd(point2), arc.b, arc.c));
   
-    var solver = pm.solve();
+    // var solver = pm.solve();
   //  var solver = pm.solve([point1._x, point1._y, point2._x, point2._y]);
-    pm.notify();
-    this.viewer.refresh();
+  //   pm.notify();
+  //   this.viewer.refresh();
   }
   
   mouseup(e) {
@@ -96,7 +108,15 @@ export class FilletTool extends Tool {
   
   breakLinkAndMakeFillet(point1, point2) {
     const pm = this.viewer.parametricManager;
-    const coi = pm.findCoincidentConstraint(point1, point2);
+    let coi = null;
+    for (let c of point1.constraints) {
+      if (c.schema.id === ConstraintDefinitions.PCoincident.id) {
+        if (c.objects.indexOf(point2) !== -1) {
+          coi = c;
+          break;
+        }
+      }
+    }
     if (coi != null) {
       pm.remove(coi);
       this.makeFillet(point1, point2);
@@ -109,23 +129,32 @@ export class FilletTool extends Tool {
   static isLine(line) {
     return line != null && line._class === 'TCAD.TWO.Segment';
   }
-  
+
   getCandidate(e) {
+    const picked = this.viewer.pick(e);
+    return this.getCandidateFromSelection(picked);
+  }
+
+  getCandidateFromSelection(picked) {
     
     let preferSketchLayer = (a, b) => (a.effectiveLayer === b.effectiveLayer)? 0 : a.effectiveLayer.name === 'sketch' ? -1 : 1;
-    
-    let picked = this.viewer.pick(e);
+
     if (picked.length > 0) {
       let res = fetch.sketchObjects(picked, true, ['TCAD.TWO.EndPoint']);
       if (res == null) return null;
       let point1 = res.sort(preferSketchLayer)[0];
       if (!FilletTool.isLine(point1.parent)) return;
-      let linked = [...point1.linked].sort(preferSketchLayer);
-      for (let i = 0; i < linked.length; i++) {
-        let point2 = linked[i];
-        if (FilletTool.isLine(point2.parent)) {
-          return [point1, point2];
+
+      const linked = [];
+      point1.visitLinked(l => {
+        if (l !== point1 && FilletTool.isLine(l.parent)) {
+          linked.push(l);
         }
+      });
+
+      if (linked.length) {
+        linked.sort(preferSketchLayer);
+        return [point1, linked[0]];
       }
     }
     return null;
@@ -133,7 +162,7 @@ export class FilletTool extends Tool {
   
   mousemove(e) {
     var needRefresh = false;
-    if (this.viewer.selected.length != 0) {
+    if (this.viewer.selected.length !== 0) {
       this.viewer.deselectAll();
       needRefresh = true;
     }
diff --git a/web/app/sketcher/tools/rectangle.js b/web/app/sketcher/tools/rectangle.js
index f2313975..a92126f7 100644
--- a/web/app/sketcher/tools/rectangle.js
+++ b/web/app/sketcher/tools/rectangle.js
@@ -53,10 +53,10 @@ export class RectangleTool extends Tool {
       this.alignSegments(p);
       
       if (this.viewer.snapped != null) {
-        this.viewer.parametricManager.linkObjects([this.rectangle[2].a, this.viewer.snapped]);
+        this.viewer.parametricManager.coincidePoints(this.rectangle[2].a, this.viewer.snapped);
       }
       if (this.firstPointSnap != null) {
-        this.viewer.parametricManager.linkObjects([this.rectangle[0].a, this.firstPointSnap]);
+        this.viewer.parametricManager.coincidePoints(this.rectangle[0].a, this.firstPointSnap);
       }
       
       this.viewer.cleanSnap();
diff --git a/web/app/sketcher/tools/tool.js b/web/app/sketcher/tools/tool.js
index 0549bf0a..635abdec 100644
--- a/web/app/sketcher/tools/tool.js
+++ b/web/app/sketcher/tools/tool.js
@@ -48,7 +48,7 @@ export class Tool {
       const snapWith = this.viewer.snapped;
       this.viewer.cleanSnap();
       p.setFromPoint(snapWith);
-      this.viewer.parametricManager.linkObjects([p, snapWith]);
+      this.viewer.parametricManager.coincidePoints(p, snapWith);
       this.viewer.parametricManager.refresh();
     }
   }