diff --git a/modules/gems/func.js b/modules/gems/func.js
index e0e91c7c..c5bffbba 100644
--- a/modules/gems/func.js
+++ b/modules/gems/func.js
@@ -34,5 +34,6 @@ export function compositeFn() {
       funcs.push(fn);
     }
   }
+  fn.push = push;
   return fn
 }
diff --git a/web/app/math/optim.js b/web/app/math/optim.js
index ca7c4bec..c87e337c 100644
--- a/web/app/math/optim.js
+++ b/web/app/math/optim.js
@@ -1,6 +1,9 @@
 import numeric from 'numeric';
 import {_vec, _matrix} from './math'
 
+const SUCCESS = 1, ITER_LIMIT = 2, SMALL_DELTA = 3, SMALL_STEP = 4, DIVERGENCE = 5, INVALID_STATE = 6;
+
+
 //Added strong wolfe condition to numeric's uncmin
 export function fmin_bfgs(f,x0,tol,gradient,maxit,callback,options) {
   var grad = numeric.gradient;
@@ -256,9 +259,10 @@ var inv = function inv(A) {
 };
 
 var _result = function(evalCount, error, returnCode) {
-  this.evalCount = evalCount;
-  this.error = error;
-  this.returnCode = returnCode;
+  return {
+    evalCount, error, returnCode,
+    success: returnCode === SUCCESS
+  };
 };
 
 var dog_leg = function (subsys, rough) {
@@ -279,7 +283,7 @@ var dog_leg = function (subsys, rough) {
   var csize = subsys.constraints.length;
 
   if (xsize == 0) {
-    return new _result(0, 0, 1);
+    return _result(0, 0, 1);
   }
 
   var vec = _vec;
@@ -330,8 +334,6 @@ var dog_leg = function (subsys, rough) {
   var iter = 0, returnCode = 0;
   //var log = [];
 
-  var SUCCESS = 1, ITER_LIMIT = 2, SMALL_DELTA = 3, SMALL_STEP = 4, DIVERGENCE = 5, INVALID_STATE = 6;
-  
   while (returnCode === 0) {
     optim.DEBUG_HANDLER(iter, err);
 
@@ -457,7 +459,7 @@ var dog_leg = function (subsys, rough) {
   }
   //log.push(returnCode);
   //window.___log(log);
-  return new _result(iter, err, returnCode);
+  return _result(iter, err, returnCode);
 };
 
 var cg = function(A, x, b, tol, maxIt) {
diff --git a/web/app/sketcher/actions/constraintActions.js b/web/app/sketcher/actions/constraintActions.js
index 99761305..1c815a7c 100644
--- a/web/app/sketcher/actions/constraintActions.js
+++ b/web/app/sketcher/actions/constraintActions.js
@@ -105,6 +105,46 @@ export default [
         pm.refresh();
       });
     }
+  },
+
+  {
+    shortName: 'Length',
+    description: 'Segment Length',
+    selectionMatcher: (selection) => matchAll(selection, Segment, 1),
+
+    invoke: ctx => {
+      const {viewer} = ctx;
+
+      const [firstSegment, ...others] = viewer.selected;
+
+      const firstConstr = new AlgNumConstraint(ConstraintDefinitions.SegmentLength, [firstSegment]);
+      firstConstr.initConstants();
+
+      editConstraint(ctx, firstConstr, () => {
+        const pm = viewer.parametricManager;
+        pm.algnNumSystem.addConstraint(firstConstr);
+        for (let other of others) {
+          pm.algnNumSystem.addConstraint(new AlgNumConstraint(ConstraintDefinitions.SegmentLength, [other], {...firstConstr.constants}));
+        }
+        pm.refresh();
+      });
+    }
+  },
+
+  {
+    shortName: 'Lock',
+    description: 'Lock Point',
+    selectionMatcher: (selection) => matchTypes(selection, EndPoint, 1),
+
+    invoke: ctx => {
+      const {viewer} = ctx;
+
+      const [point] = viewer.selected;
+
+      const constr = new AlgNumConstraint(ConstraintDefinitions.LockPoint, [point]);
+      constr.initConstants();
+      editConstraint(ctx, constr, () => viewer.parametricManager.addAlgNum(constr));
+    }
   }
 
 ];
diff --git a/web/app/sketcher/constr/ANConstraints.js b/web/app/sketcher/constr/ANConstraints.js
index d28a207a..3aaf9df1 100644
--- a/web/app/sketcher/constr/ANConstraints.js
+++ b/web/app/sketcher/constr/ANConstraints.js
@@ -111,18 +111,13 @@ export const ConstraintDefinitions = indexById([
         initialValue: (constraint) => {
           const [a, b] = constraint.objects;
           return distanceAB(a, b);
-        }
+        },
       }
     },
 
-    defineParamsScope: ([pt, segment], callback) => {
-      pt.visitParams(callback);
-      callback(segment.params.ang);
-      callback(segment.params.w);
-    },
-
-    collectResiduals: (residuals, params, {distance}) => {
-      residuals.push([R_DistancePP, params, [distance]]);
+    defineParamsScope: ([pt1, pt2], callback) => {
+      pt1.visitParams(callback);
+      pt2.visitParams(callback);
     },
 
     collectPolynomials: (polynomials, [x1, y1, x2, y2], {distance}) => {
@@ -201,6 +196,85 @@ export const ConstraintDefinitions = indexById([
     },
   },
 
+  {
+    id: 'SegmentLength',
+    name: 'Segment Length',
+    constants: {
+      length: {
+        type: 'number',
+        description: 'length of the segment',
+        initialValue: (constraint) => {
+          const [segment] = constraint.objects;
+          const dx = segment.b.x - segment.a.x;
+          const dy = segment.b.y - segment.a.y;
+          return Math.sqrt(dx*dx + dy*dy);
+        },
+
+        // transform: length => length * length
+      }
+    },
+
+    defineParamsScope: ([segment], callback) => {
+      callback(segment.params.t);
+    },
+
+    collectPolynomials: (polynomials, [t], {length}) => {
+      polynomials.push(new Polynomial( - length).monomial(1).term(t, POW_1_FN));
+    },
+  },
+
+  {
+    id: 'Polar',
+    name: 'Polar Coordinate',
+
+    defineParamsScope: ([segment, originPt, targetPt], callback) => {
+      callback(segment.params.ang);
+      callback(segment.params.t);
+      originPt.visitParams(callback);
+      targetPt.visitParams(callback);
+    },
+
+    collectPolynomials: (polynomials, [ang, t, x1, y1, x2, y2]) => {
+
+
+      //  v = [sin(ang), - cos(ang)]
+      //  v * t = pt2 -  pt1
+
+      //sin(ang) * t  - x2 + x1
+      //-cos(ang) * t  - y2 + y1
+
+      polynomials.push(new Polynomial().monomial()  .term(ang, SIN_FN).term(t, POW_1_FN).monomial(-1).term(x2, POW_1_FN).monomial(1).term(x1, POW_1_FN));
+      polynomials.push(new Polynomial().monomial(-1).term(ang, COS_FN).term(t, POW_1_FN).monomial(-1).term(y2, POW_1_FN).monomial(1).term(y1, POW_1_FN));
+    },
+  },
+
+
+  {
+    id: 'LockPoint',
+    name: 'Lock Point',
+    constants: {
+      x: {
+        type: 'number',
+        description: 'X Coordinate',
+        initialValue: (constraint) => constraint.objects[0].x,
+      },
+      y: {
+        type: 'number',
+        description: 'y Coordinate',
+        initialValue: (constraint) => constraint.objects[0].y,
+      }
+    },
+
+    defineParamsScope: ([pt], callback) => {
+      pt.visitParams(callback);
+    },
+
+    collectPolynomials: (polynomials, [px, py], {x, y}) => {
+      polynomials.push(new Polynomial(-x).monomial().term(px, POW_1_FN));
+      polynomials.push(new Polynomial(-y).monomial().term(py, POW_1_FN));
+    },
+  }
+
 ]);
 
 export class AlgNumConstraint {
diff --git a/web/app/sketcher/constr/AlgNumSystem.js b/web/app/sketcher/constr/AlgNumSystem.js
index 50b62576..0c97e759 100644
--- a/web/app/sketcher/constr/AlgNumSystem.js
+++ b/web/app/sketcher/constr/AlgNumSystem.js
@@ -11,7 +11,7 @@ export class AlgNumSubSystem {
 
   generator = NOOP;//new BoundaryObjectsGenerator();
 
-  constraints = [];
+  allConstraints = [];
 
   ownParams = new Set();
 
@@ -21,6 +21,7 @@ export class AlgNumSubSystem {
 
   beingSolvedParams = new Set();
 
+  eliminatedParams = new Map();
 
   // generators = [];
   subSystems = []; //subsystems are generated by generators only
@@ -28,13 +29,31 @@ export class AlgNumSubSystem {
   polynomials = [];
   substitutedParams = [];
   polyToConstr = new Map();
+
   conflicting = new Set();
   redundant  = new Set();
 
+  snapshot = new Map();
+
+  dof = 0;
+
   SubSystem(generator) {
     this.generator = generator;
   }
 
+
+  get fullyConstrained() {
+    return this.dof === 0;
+  }
+
+  validConstraints(callback) {
+    this.allConstraints.forEach(c => {
+      if (!this.conflicting.has(c)) {
+        callback(c);
+      }
+    });
+  }
+
   addConstraint(constraint, _ancestorParams) {
 
     if (this.canBeAdded(constraint.params)) {
@@ -42,20 +61,73 @@ export class AlgNumSubSystem {
       // this.constraints
     }
 
-    this.constraints.push(constraint);
+    this.makeSnapshot();
+
+    this.allConstraints.push(constraint);
+
+    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);
+      }
+    }
+
+    if (this.isConflicting(constraint)) {
+      this.rollback();
+    // } else if (this.fullyConstrained) {
+    //   this.rollback();
+    //   this.conflicting.add(constraint);
+    //   this.redundant.add(constraint);
+    } else {
+      this.updateDOF();
+      this.updateFullyConstrainedObjects();
+    }
+
+  }
+
+  isConflicting(constraint) {
+    return this.conflicting.has(constraint);
+  }
+
+  updateDOF() {
+
+    let vars = 0;
+    let equations = 0;
+
+    this.validConstraints(c => {
+      equations ++;
+      c.params.forEach(p => {
+        if (!this.readOnlyParams.has(p)) {
+          vars++
+        }
+      })
+    });
+
+    this.dof = vars - equations;
+  }
+
+  makeSnapshot() {
+    this.snapshot.clear();
+    this.validConstraints(c => c.params.forEach(p => this.snapshot.set(p, p.get())));
+  }
+
+  rollback() {
+    this.snapshot.forEach((val, param) => param.set(val));
   }
 
   reset() {
     this.polynomials = [];
     this.substitutedParams = [];
-    this.polyToConstr.clear();
-    this.conflicting.clear();
-    this.redundant.clear();
+    this.eliminatedParams.clear();
     this.beingSolvedParams.clear();
+    this.polyToConstr.clear();
   }
 
   evaluatePolynomials() {
-    this.constraints.forEach(c => {
+    this.validConstraints(c => {
       c.collectPolynomials(this.polynomials);
       this.polynomials.forEach(p => this.polyToConstr.set(p, c))
     });
@@ -63,11 +135,6 @@ export class AlgNumSubSystem {
     console.log('reducing system:');
     this.polynomials.forEach(p => console.log(p.toString()));
 
-    const toEliminate = Array.from(this.readOnlyParams);
-
-    const toSubstitute = [];
-    const linearSub = [];
-
     let requirePass = true;
 
     while (requirePass) {
@@ -79,74 +146,74 @@ export class AlgNumSubSystem {
         }
 
         if (polynomial.monomials.length === 0) {
-          if (!eqEps(polynomial.constant, 0)) {
-            this.conflicting.add(this.polyToConstr.get(polynomial));
+          this.conflicting.add(this.polyToConstr.get(polynomial));
+          console.log("CONFLICT: " + polynomial.toString());
+          if (eqEps(polynomial.constant, 0)) {
+            this.redundant.add(this.polyToConstr.get(polynomial));
+            console.log("REDUNDANT");
           }
           this.polynomials[i] = null;
-        } else if (polynomial.monomials.length === 1) {
+        } else if (polynomial.isLinear && polynomial.monomials.length === 1) {
           const monomial = polynomial.monomials[0];
           const terms = monomial.terms;
           if (terms.length === 1) {
             const term = terms[0];
             if (term.fn.degree === 1) {
-              term.param.set(- polynomial.constant / monomial.constant);
-              toEliminate.push(term.param);
+              const p = term.param;
+              const val = - polynomial.constant / monomial.constant;
+              p.set(val);
+
+              this.eliminatedParams.set(p, val);
+
+              for (let polynomial of this.polynomials) {
+                if (polynomial) {
+                  polynomial.eliminate(p, val);
+                }
+              }
+
+              requirePass = true;
             }
           }
 
           this.polynomials[i] = null;
         } else if (polynomial.monomials.length === 2 && polynomial.isLinear) {
           const [m1, m2] = polynomial.monomials;
+          let p1 = m1.linearParam;
+          let p2 = m2.linearParam;
 
           const constant = - m2.constant / m1.constant;
           if (eqEps(polynomial.constant, 0)) {
-            toSubstitute.push([m1.linearParam, m2.linearParam, constant]);
-            this.substitutedParams.push([m1.linearParam, new Polynomial().monomial(constant).term(m2.linearParam, POW_1_FN)]);
-          } else {
-            linearSub.push([m1.param, m2.param, constant, - polynomial.constant / m1.constant]);
-          }
-          this.polynomials[i] = null;
-        }
-      }
 
-      while (toEliminate.length) {
-        requirePass = true;
-        const param = toEliminate.pop();
-        for (let polynomial of this.polynomials) {
-          if (polynomial) {
-            polynomial.eliminate(param, param.get());
-          }
-        }
-      }
-      while (toSubstitute.length) {
-        requirePass = true;
-        const [param, toParam, dotConstant] = toSubstitute.pop();
-        for (let polynomial of this.polynomials) {
-          if (polynomial) {
-            polynomial.substitute(param, toParam, dotConstant);
-          }
-        }
-      }
-
-      if (linearSub.length) {
-        while (linearSub.length) {
-          const [param, toParam, k, b] = linearSub.pop();
-
-          let transaction = compositeFn();
-          for (let polynomial of this.polynomials) {
-            if (polynomial) {
-              const polyTransaction = polynomial.linearSubstitution(param, toParam, k, b);
-              if (!polyTransaction) {
-                transaction = null;
-                break;
+            for (let polynomial of this.polynomials) {
+              if (polynomial) {
+                polynomial.substitute(p1, p2, constant);
               }
-              transaction.push(polyTransaction);
-              transaction.push(() => this.substitutedParams.push(param, new Polynomial(b).monomial(k).term(toParam, POW_1_FN)));
             }
-          }
-          if (transaction) {
+            this.substitutedParams.push([p1, new Polynomial().monomial(constant).term(p2, POW_1_FN)]);
+            this.polynomials[i] = null;
             requirePass = true;
-            transaction();
+          } else {
+            const b = - polynomial.constant / m1.constant;
+
+            let transaction = compositeFn();
+            for (let polynomial of this.polynomials) {
+              if (polynomial) {
+                const polyTransaction = polynomial.linearSubstitution(p1, p2, constant, b);
+                if (!polyTransaction) {
+                  transaction = null;
+                  break;
+                }
+                transaction.push(polyTransaction);
+                transaction.push(() => {
+                  this.substitutedParams.push([p1, new Polynomial(b).monomial(constant).term(p2, POW_1_FN)]);
+                  this.polynomials[i] = null;
+                });
+              }
+            }
+            if (transaction) {
+              transaction();
+              requirePass = true;
+            }
           }
         }
       }
@@ -168,12 +235,13 @@ export class AlgNumSubSystem {
 
     this.evaluatePolynomials();
 
+    // this.polynomialClusters = splitByIsolatedClusters(this.polynomials);
+
     console.log('solving system:');
     this.polynomials.forEach(p => console.log(p.toString()));
     console.log('with respect to:');
     this.substitutedParams.forEach(([x, expr]) => console.log('X' + x.id  + ' = ' + expr.toString()));
 
-
     const residuals = [];
 
     this.polynomials.forEach(p => residuals.push(p.asResidual()));
@@ -189,6 +257,63 @@ export class AlgNumSubSystem {
     this.numericalSolver = prepare(residuals);
   }
 
+  splitByIsolatedClusters(polynomials) {
+
+    const graph = [polynomials.length];
+    const params = [];
+    const paramMap = new Map();
+    polynomials.forEach((pl, i) => pl.visitParams(p => {
+      let pIndex = paramMap.get(p);
+      if (pIndex === undefined) {
+        pIndex = paramMap.size;
+        paramMap.set(p, pIndex);
+        params.push(p);
+      }
+      graph[i][pIndex] = 1;
+    }));
+
+    const visited = new Set();
+    const clusters = [];
+
+    for (let param of params) {
+      if (visited.has(param)) {
+        continue
+      }
+      const stack = [param];
+      const isolation = [];
+      while (stack.length) {
+        const p = stack.pop();
+        if (visited.has(p)) {
+          continue;
+        }
+        isolation.push(p);
+        const index = paramMap.get(p);
+        for (let i = 0; i < graph.length; ++i) {
+          if (graph[i][index] === 1) {
+            for (let j = 0; j < params.length; j ++) {
+              if (j !== index) {
+                stack.push(params[j]);
+              }
+            }
+          }
+        }
+      }
+      if (isolation.length) {
+        clusters.push(new Cluster(isolation));
+      }
+    }
+
+    return clusters;
+  }
+
+  solveRough() {
+    this.solve(true);
+  }
+
+  solveFine() {
+    this.solve(false);
+  }
+
 
   solve(rough) {
     this.generator();
@@ -197,7 +322,15 @@ export class AlgNumSubSystem {
       solverParam.set(solverParam.objectParam.get());
     });
 
-    this.numericalSolver.solveSystem(rough);
+    const solveStatus = this.numericalSolver.solveSystem(rough);
+    if (!rough) {
+      this.solveStatus = solveStatus;
+    }
+    console.log('numerical result: ' + solveStatus.success);
+
+    for (let [p, val] of this.eliminatedParams) {
+      p.set(val);
+    }
 
     this.beingSolvedParams.forEach(solverParam => {
       solverParam.objectParam.set(solverParam.get());
@@ -208,6 +341,27 @@ export class AlgNumSubSystem {
     }
   }
 
+  updateFullyConstrainedObjects() {
+
+
+
+    this.validConstraints(c => {
+
+      c.objects.forEach(obj => {
+
+        let allLocked = true;
+
+        obj.visitParams(p => {
+
+          if (!this.eliminatedParams.has(p)) {
+            allLocked = false;
+          }
+        });
+
+        obj.fullyConstrained = allLocked;
+      });
+    });
+  }
 
 
   canBeAdded(subjectParams, ancestorParams) {
@@ -223,6 +377,41 @@ export class AlgNumSubSystem {
 }
 
 
+class Cluster {
+
+  constructor(polynomials) {
+    this.polynomials = polynomials;
+    this.beingSolvedParams = new Set();
+    const residuals = [];
+
+    this.polynomials.forEach(p => residuals.push(p.asResidual()));
+
+    for (let residual of residuals) {
+      residual.params.forEach(solverParam => {
+        if (!this.beingSolvedParams.has(solverParam)) {
+          solverParam.reset(solverParam.objectParam.get());
+          this.beingSolvedParams.add(solverParam);
+        }
+      });
+    }
+
+  }
+
+  solve(rough) {
+    this.beingSolvedParams.forEach(solverParam => {
+      solverParam.set(solverParam.objectParam.get());
+    });
+
+    this.solveStatus = this.numericalSolver.solveSystem(rough);
+
+    this.beingSolvedParams.forEach(solverParam => {
+      solverParam.objectParam.set(solverParam.get());
+    });
+  }
+
+}
+
+
 export class AlgNumSystem {
   constraints = [];
   generators = [];
diff --git a/web/app/sketcher/constr/polynomial.js b/web/app/sketcher/constr/polynomial.js
index da39fac8..35a85d84 100644
--- a/web/app/sketcher/constr/polynomial.js
+++ b/web/app/sketcher/constr/polynomial.js
@@ -38,11 +38,16 @@ export class Polynomial {
 
   substitute(param, toParam, dotConstant) {
     for (let m of this.monomials) {
+      let touched = false;
       for (let i = 0; i < m.terms.length; ++i) {
         if (m.terms[i].param === param) {
           m.substitute(i, toParam, dotConstant);
+          touched = true;
         }
       }
+      if (touched) {
+        m.mergeTerms();
+      }
     }
   }
 
@@ -161,6 +166,14 @@ export class Polynomial {
 
   }
 
+  visitParams(callback) {
+    for (let m of this.monomials) {
+      for (let t of m.terms) {
+        callback(t.param);
+      }
+    }
+  }
+
   toString() {
 
     return this.monomials.map(m => {
@@ -227,8 +240,12 @@ export class Monomial {
     this.terms.splice(i, 1);
   }
 
-  substitute(i, toParam, dotConstant) {
+  substitute(index, toParam, dotConstant) {
+    this.terms[index].param = toParam;
     this.constant *= dotConstant;
+  }
+
+  mergeTerms() {
     let wasMerge = false;
     for (let i = 0; i < this.terms.length; ++i) {
       const merger = this.terms[i];
@@ -250,7 +267,6 @@ export class Monomial {
     if (wasMerge) {
       this.terms = this.terms.filter(t => t);
     }
-
   }
 
   equalVars(other) {
@@ -321,6 +337,7 @@ export class ToThePowerFunction {
   }
 
   constructor(degree, fn, d1) {
+    this.degree = degree;
     this.fn = fn;
     this.d1 = d1;
     this.id = '^' + degree;
@@ -358,10 +375,11 @@ export class FreeFunction {
 
   fn;
 
-  constructor(fn, d1, id) {
+  constructor(fn, d1, id, linearSubstitutionFn) {
     this.fn = fn;
     this.d1 = d1;
     this.id = id;
+    this.linearSubstitutionFn = linearSubstitutionFn || null;
   }
 
   apply(x) {
@@ -381,7 +399,7 @@ export class FreeFunction {
   }
 
   linearSubstitution(k, x, b) {
-    return null;
+    return this.linearSubstitutionFn(k, x, b);
   }
 
 }
@@ -415,7 +433,7 @@ export class CosineOfSum {
   }
 
   render(x) {
-    return 'cos(' + this.k.toFixed(2) + x + ' + ' + this.b.toFixed(2) + ')';
+    return 'cos(' + this.k.toFixed(2) + '*' + x + ' + ' + this.b.toFixed(2) + ')';
   }
 
 }
@@ -449,7 +467,7 @@ export class SineOfSum {
   }
 
   render(x) {
-    return 'sin(' + this.k.toFixed(2) + x + ' + ' + this.b.toFixed(2) + ')';
+    return 'sin(' + this.k.toFixed(2) + '*' + x + ' + ' + this.b.toFixed(2) + ')';
   }
 }
 
diff --git a/web/app/sketcher/io.js b/web/app/sketcher/io.js
index 8a854c70..537705e3 100644
--- a/web/app/sketcher/io.js
+++ b/web/app/sketcher/io.js
@@ -400,7 +400,7 @@ IO.prototype._serializeSketch = function(metadata) {
   }
 
   sketch.constraints = [];
-  const systemConstraints = this.viewer.parametricManager.algnNumSystem.constraints;
+  const systemConstraints = this.viewer.parametricManager.algnNumSystem.allConstraints;
   for (let sc of systemConstraints) {
     if (!sc.internal) {
       sketch.constraints.push(sc.write());
diff --git a/web/app/sketcher/parametric.js b/web/app/sketcher/parametric.js
index 687fa030..92ced3c4 100644
--- a/web/app/sketcher/parametric.js
+++ b/web/app/sketcher/parametric.js
@@ -105,6 +105,10 @@ class ParametricManager {
     this.refresh();
   }
 
+  coincidePoints(pt1, pt2) {
+    this.addAlgNum(new AlgNumConstraint(ConstraintDefinitions.PCoincident, [pt1, pt2]));
+  }
+
 }
 
 ParametricManager.prototype.createConstantResolver = function() {
diff --git a/web/app/sketcher/shapes/segment.js b/web/app/sketcher/shapes/segment.js
index e4c7285f..1390a816 100644
--- a/web/app/sketcher/shapes/segment.js
+++ b/web/app/sketcher/shapes/segment.js
@@ -47,18 +47,15 @@ export class Segment extends SketchObject {
 
     let ang = Math.atan2(ny, nx);
 
-    if (this.ang !== undefined && Math.abs(ang - this.ang) > Math.PI) {
-      ang = Math.atan2(-ny, -nx);
-    }
-
     this.params.ang.set(ang||0);
     this.params.w.set(nx * this.a.x + ny * this.a.y);
+    this.params.t.set(l);
   }
 
   stabilize(viewer) {
     this.syncGeometry();
     const c1 = new AlgNumConstraint(ConstraintDefinitions.PointOnLine, [this.a, this]);
-    const c2 = new AlgNumConstraint(ConstraintDefinitions.PointOnLine, [this.b, this]);
+    const c2 = new AlgNumConstraint(ConstraintDefinitions.Polar, [this, this.a, this.b]);
     c1.internal = true;
     c2.internal = true;
     viewer.parametricManager.addAlgNum(c1);
diff --git a/web/app/sketcher/shapes/sketch-object.js b/web/app/sketcher/shapes/sketch-object.js
index b1596fc4..52bfe303 100644
--- a/web/app/sketcher/shapes/sketch-object.js
+++ b/web/app/sketcher/shapes/sketch-object.js
@@ -1,6 +1,7 @@
 import {Generator} from '../id-generator'
 import {Shape} from './shape'
 import {Types} from '../io';
+import {Styles} from "../styles";
 
 export class SketchObject extends Shape {
   constructor() {
@@ -11,6 +12,7 @@ export class SketchObject extends Shape {
     this.children = [];
     this.linked = [];
     this.layer = null;
+    this.fullyConstrained = false;
   }
 
   normalDistance(aim, scale) {
@@ -86,8 +88,12 @@ export class SketchObject extends Shape {
       ctx.save();
       viewer.setStyle(this.marked, ctx);
     }
+    if (this.fullyConstrained) {
+      ctx.save();
+      viewer.setStyle(Styles.FULLY_CONSTRAINED, ctx);
+    }
     this.drawImpl(ctx, scale, viewer);
-    if (this.marked != null) ctx.restore();
+    if (this.marked != null || this.fullyConstrained) ctx.restore();
   }
   
   copy() {
diff --git a/web/app/sketcher/styles.js b/web/app/sketcher/styles.js
index 8542ea9e..0f3ccf00 100644
--- a/web/app/sketcher/styles.js
+++ b/web/app/sketcher/styles.js
@@ -39,6 +39,12 @@ export const Styles = {
     fillStyle : "#000000"
   },
 
+  FULLY_CONSTRAINED: {
+    lineWidth : 2,
+    strokeStyle : "#d7e6ff",
+    fillStyle : "#424e56"
+  },
+
   CONSTRUCTION : {
     lineWidth : 1,
     strokeStyle : "#aaaaaa",
diff --git a/web/app/sketcher/tools/drag.js b/web/app/sketcher/tools/drag.js
index c8cef0b4..2d9b253b 100644
--- a/web/app/sketcher/tools/drag.js
+++ b/web/app/sketcher/tools/drag.js
@@ -23,7 +23,7 @@ export class DragTool extends Tool {
     //   this.lockedValues[i + 1] = this._point.y - this.lockedShifts[i + 1];
     // }
     this.obj.translate(dx, dy);
-
+    (this.obj.parent || this.obj).syncGeometry();
     if (!Tool.dumbMode(e)) {
       this.viewer.parametricManager.algnNumSystem.solve(true);
     }
diff --git a/web/app/sketcher/tools/segment.js b/web/app/sketcher/tools/segment.js
index ca55ca77..cb196281 100644
--- a/web/app/sketcher/tools/segment.js
+++ b/web/app/sketcher/tools/segment.js
@@ -19,7 +19,7 @@ export class AddSegmentTool extends Tool {
   }
 
   mousemove(e) {
-    var p = this.viewer.screenToModel(e);
+    let p = this.viewer.screenToModel(e);
     if (this.line != null) {
       this.viewer.snap(p.x, p.y, [this.line.a, this.line.b]);
       this.line.b.x = p.x;
@@ -35,7 +35,7 @@ export class AddSegmentTool extends Tool {
     if (this.line == null) {
       const b = this.viewer.screenToModel(e);
       let a = b;
-      var needSnap = false;
+      let needSnap = false;
       if (this.viewer.snapped != null) {
         a = this.viewer.snapped;
         this.viewer.cleanSnap();
@@ -43,7 +43,7 @@ export class AddSegmentTool extends Tool {
       }
       this.line = this.viewer.addSegment(a.x, a.y, b.x, b.y, this.viewer.activeLayer);
       if (needSnap) {
-        this.line.a.coincideWith(a);
+        this.viewer.parametricManager.coincidePoints(this.line.a, a);
       }
       this.firstPointPicked();
       this.viewer.refresh();
@@ -53,7 +53,7 @@ export class AddSegmentTool extends Tool {
         this.viewer.cleanSnap();
         this.line.b.x = p.x;
         this.line.b.y = p.y;
-        this.line.b.coincideWith(p);
+        this.viewer.parametricManager.coincidePoints(this.line.b, p);
       }
       this.nextPointPicked();
     }
@@ -61,10 +61,11 @@ export class AddSegmentTool extends Tool {
   
   nextPointPicked() {
     this.pointPicked(this.line.b.x, this.line.b.y);
+    this.line.stabilize(this.viewer);
     if (this.multi) {
       const b = this.line.b;
       this.line = this.viewer.addSegment(b.x, b.y, b.x, b.y, this.viewer.activeLayer);
-      this.line.a.coincideWith(b);
+      this.viewer.parametricManager.coincidePoints(this.line.a, b);
     } else {
       this.restart()
     }
diff --git a/web/app/sketcher/viewer2d.js b/web/app/sketcher/viewer2d.js
index bb8047c7..52c35c82 100644
--- a/web/app/sketcher/viewer2d.js
+++ b/web/app/sketcher/viewer2d.js
@@ -121,7 +121,6 @@ class Viewer {
     var b = new EndPoint(x2, y2);
     var line = new Segment(a, b);
     layer.add(line);
-    line.stabilize(this);
     return line;
   };