diff --git a/Canvas.cpp b/Canvas.cpp
index 556dbf6..c613cbb 100644
--- a/Canvas.cpp
+++ b/Canvas.cpp
@@ -1,4 +1,6 @@
 #include "Canvas.h"
+#define WIDGET_POSITION event->pos()
+#define UCS_POSITION screenToLogical(WIDGET_POSITION)
 
 // ===================================================================
 // Вспомогательные функции
@@ -78,7 +80,6 @@ void Canvas::changeMode(Mode _mode)
 
 Line* Canvas::findAt(QPointF& pos, qreal tolerance)
 {
-    // TODO: реализовать проверку, находится ли точка на линии
     for (Line* line : lines) {
         if (line->contains(pos, tolerance)) {
             return line;
@@ -136,48 +137,62 @@ bool Canvas::areAlreadyParallel(Line* l1, Line* l2)
     return parallelPairs.count(makeOrderedPair<LinePair>(l1, l2));
 }
 
+bool Canvas::areAlreadyPerpendicular(Line* line1, Line* line2)
+{
+    return perpendicularPairs.count(makeOrderedPair<LinePair>(line1, line2));
+}
+
 // ===================================================================
 // Методы работы с ограничениями
 // ===================================================================
 
-void Canvas::remove_constraints()
+// TODO - переделать в bool для отображения статуса выполнения
+void Canvas::remove_constraint(int tag)
 {
+    auto it = C_Info.find(tag);
+    if (it == C_Info.end()) return;
+
+    ConstraintInfo info = it->second;
+
     // Удаляем ограничение из солвера
-    sys.clearByTag(constraints_count - 1);
+    sys.clearByTag(tag);
 
     // Удаляем из соответствующих контейнеров в зависимости от типа ограничения
-    switch (lastConstraint.mode) {
+    switch (info.mode) {
     case Mode::Horizontal: {
-        if (auto* pair = std::get_if<PointPair>(&lastConstraint.data)) {
+        if (auto* pair = std::get_if<PointPair>(&info.data)) {
             HORIZ_pairs.erase(*pair);
         }
         break;
     }
     case Mode::Vertical: {
-        if (auto* pair = std::get_if<PointPair>(&lastConstraint.data)) {
+        if (auto* pair = std::get_if<PointPair>(&info.data)) {
             VERT_pairs.erase(*pair);
         }
         break;
     }
     case Mode::Parallel: {
-        if (auto* pair = std::get_if<LinePair>(&lastConstraint.data)) {
+        if (auto* pair = std::get_if<LinePair>(&info.data)) {
             parallelPairs.erase(*pair);
         }
         break;
     }
     case Mode::Coincedent: {
-        if (auto* pair = std::get_if<PointPair>(&lastConstraint.data)) {
+        if (auto* pair = std::get_if<PointPair>(&info.data)) {
             P2Ppairs.erase(*pair);
         }
         break;
     }
+    case Mode::Perpendicular: {
+        if (auto* pair = std::get_if<LinePair>(&info.data)) {
+            perpendicularPairs.erase(*pair);
+        }
+        break;
+    }
     default:
         break;
     }
-
-    // Сбрасываем информацию о последнем ограничении
-    lastConstraint.mode = Mode::None;
-    constraints_count--;
+    C_Info.erase(it);
 }
 
 // ===================================================================
@@ -244,17 +259,15 @@ void Canvas::mousePressEvent(QMouseEvent* event)
                 sys.addConstraintHorizontal(*found, constraints_count++);
                 auto pair = makeOrderedPair<PointPair>(found->start_ref, found->end_ref);
                 HORIZ_pairs.insert(pair);
-                lastConstraint.mode = Mode::Horizontal;
-                lastConstraint.data = pair;
+                C_Info[constraints_count - 1] = { Mode::Horizontal, pair };
             }
             else {
                 sys.addConstraintVertical(*found, constraints_count++);
                 auto pair = makeOrderedPair<PointPair>(found->start_ref, found->end_ref);
                 VERT_pairs.insert(pair);
-                lastConstraint.mode = Mode::Vertical;
-                lastConstraint.data = pair;
+                C_Info[constraints_count - 1] = { Mode::Vertical, pair };
             }
-            update();
+            solve_for_canvas();
             after_constraint = true;
         }
         mode = Mode::None;
@@ -315,7 +328,7 @@ void Canvas::mousePressEvent(QMouseEvent* event)
                 mode = Mode::None;
                 QMessageBox::critical(this, "WHOOPS",
                     "Sorry, your line is very short", QMessageBox::Ok);
-                update();
+                solve_for_canvas();
                 return;
             }
 
@@ -330,7 +343,7 @@ void Canvas::mousePressEvent(QMouseEvent* event)
             obj_count++;
             after_constraint = true;
         }
-        update();
+        solve_for_canvas();
         return;
     }
 
@@ -340,21 +353,21 @@ void Canvas::mousePressEvent(QMouseEvent* event)
 
         if (!found) {
             current_line = nullptr;
-            update();
+            solve_for_canvas();
             return;
         }
 
         // Первый клик: выбираем первую линию
         if (!current_line) {
             current_line = found;
-            update();
+            solve_for_canvas();
             return;
         }
 
         // Повторный клик на ту же линию: сброс выбора
         if (found == current_line) {
             current_line = nullptr;
-            update();
+            solve_for_canvas();
             return;
         }
 
@@ -363,13 +376,12 @@ void Canvas::mousePressEvent(QMouseEvent* event)
             auto pair = makeOrderedPair<LinePair>(found, current_line);
             sys.addConstraintParallel(*found, *current_line, constraints_count++);
             parallelPairs.insert(pair);
-            lastConstraint.mode = Mode::Parallel;
-            lastConstraint.data = pair;
+            C_Info[constraints_count - 1] = { Mode::Parallel, pair };
 
             current_line = nullptr;
             mode = Mode::None;
             after_constraint = true;
-            update();
+            solve_for_canvas();
         }
         else {
             // Линии уже параллельны - сообщаем об ошибке
@@ -383,7 +395,7 @@ void Canvas::mousePressEvent(QMouseEvent* event)
                 QMessageBox::Ok
             );
             current_line = nullptr;
-            update();
+            solve_for_canvas();
             return;
         }
     }
@@ -393,21 +405,21 @@ void Canvas::mousePressEvent(QMouseEvent* event)
         Point* clickedPoint = findPointAt(scene);
         if (!clickedPoint) {
             firstPoint = nullptr;
-            update();
+            solve_for_canvas();
             return;
         }
 
         // Первый клик: выбираем первую точку
         if (!firstPoint) {
             firstPoint = clickedPoint;
-            update();
+            solve_for_canvas();
             return;
         }
 
         // Повторный клик на ту же точку: сброс выбора
         if (clickedPoint == firstPoint) {
             firstPoint = nullptr;
-            update();
+            solve_for_canvas();
             return;
         }
 
@@ -426,7 +438,7 @@ void Canvas::mousePressEvent(QMouseEvent* event)
             QMessageBox::critical(this, QString("NO!"), QString("P2P failed"));
             firstPoint = nullptr;
             mode = Mode::None;
-            update();
+            solve_for_canvas();
             return;
         }
 
@@ -434,15 +446,61 @@ void Canvas::mousePressEvent(QMouseEvent* event)
         sys.addConstraintP2PCoincident(*clickedPoint, *firstPoint, constraints_count++);
         auto pair = makeOrderedPair<PointPair>(clickedPoint, firstPoint);
         P2Ppairs.insert(pair);
-        lastConstraint.mode = Mode::Coincedent;
-        lastConstraint.data = pair;
+        C_Info[constraints_count - 1] = { Mode::Coincedent, pair };
 
         firstPoint = nullptr;
         mode = Mode::None;
         after_constraint = true;
-        update();
+        solve_for_canvas();
         return;
     }
+
+    else if (mode == Mode::Perpendicular) {
+        Line* found = findAt(scene);
+
+        if (!found) {
+            current_line = nullptr;
+            solve_for_canvas();
+            return;
+        }
+
+        // Первый клик: выбираем первую линию
+        if (!current_line) {
+            current_line = found;
+            solve_for_canvas();
+            return;
+        }
+
+        // Повторный клик на ту же линию: сброс выбора
+        if (found == current_line) {
+            current_line = nullptr;
+            solve_for_canvas();
+            return;
+        }
+
+        if (!areAlreadyPerpendicular(found, current_line)) {
+            auto pair = makeOrderedPair<LinePair>(found, current_line);
+            sys.addConstraintPerpendicular(*found, *current_line, constraints_count++);
+            perpendicularPairs.insert(pair);
+            C_Info[constraints_count - 1] = { Mode::Perpendicular, pair };
+
+            current_line = nullptr;
+            mode = Mode::None;
+            after_constraint = true;
+            solve_for_canvas();
+        }
+        else {
+
+            QMessageBox::warning(this,
+                QString("Wrong"),
+                QString("Perpendicular lines can not be more perpendicular!"),
+                QMessageBox::Ok
+            );
+            current_line = nullptr;
+            solve_for_canvas();
+            return;
+        }
+    }
 }
 
 void Canvas::mouseMoveEvent(QMouseEvent* event)
@@ -451,8 +509,18 @@ void Canvas::mouseMoveEvent(QMouseEvent* event)
     if (draggedPoint) {
         QPointF pos = UCS_POSITION - dragOffset;
 
-        auto coincidentGroup = getCoincidentGroup(draggedPoint);
+        *draggedPoint->x = pos.x();
+        *draggedPoint->y = pos.y();
 
+        // TODO
+        for (Point* pair : points) {
+            if (areCoincident(draggedPoint, pair)) {
+                *pair->x = pos.x();
+                *pair->y = pos.y();
+            }
+        }
+
+        auto coincidentGroup = getCoincidentGroup(draggedPoint);
         for (Point* pt : coincidentGroup) {
             *pt->x = pos.x();
             *pt->y = pos.y();
@@ -469,9 +537,16 @@ void Canvas::mouseMoveEvent(QMouseEvent* event)
             }
         }
 
-        *draggedPoint->x = pos.x();
-        *draggedPoint->y = pos.y();
-        update();
+        for (Point* other : points) {
+            if (areHorizontalVertical(draggedPoint, other, true)) {
+                *other->x = pos.x();
+            }
+            if (areHorizontalVertical(draggedPoint, other, false)) {
+                *other->y = pos.y();
+            }
+        }
+
+        solve_for_canvas();
     }
 
     // ====================== Перемещение линии ======================
@@ -503,7 +578,7 @@ void Canvas::mouseMoveEvent(QMouseEvent* event)
                 }
             }
         }
-        update();
+        solve_for_canvas();
     }
     #ifdef _DEBUG
     else
@@ -517,12 +592,12 @@ void Canvas::mouseReleaseEvent(QMouseEvent* event)
 
     if (draggedPoint) {
         draggedPoint = nullptr;
-        update();
+        solve_for_canvas();
     }
 
     if (draggedLine) {
         draggedLine = nullptr;
-        update();
+        solve_for_canvas();
     }
 }
 
@@ -543,22 +618,6 @@ void Canvas::paintEvent(QPaintEvent* event)
     p.drawLine(-5, 0, 5, 0);
     p.drawLine(0, -5, 0, 5);
 
-
-    // ====================== Решение системы уравнений ======================
-    if (!params.empty()) {
-        int res = sys.solve(params);
-        if (res == SolveStatus::Success || res == SolveStatus::Converged) {
-            sys.applySolution();
-        }
-        else if (res == SolveStatus::Failed && after_constraint) {
-            // Ошибка решения: удаляем последнее добавленное ограничение
-            QMessageBox::warning(this, QString("Error!"),
-                QString("Last constraint is unavailable!"));
-            remove_constraints();
-        }
-        after_constraint = false;
-    }
-
     // ====================== Отрисовка линий ======================
     for (Line* line : lines) {
         bool isSelected = (mode == Mode::Parallel && line == current_line);
@@ -651,3 +710,30 @@ std::vector<Point*> Canvas::getCoincidentGroup(Point* p)
     }
     return group;
 }
+
+void Canvas::solve_for_canvas()
+{
+    bool flag = false;
+    int res = sys.solve(params);
+    if (res != SolveStatus::Success && res != SolveStatus::Converged) {
+        flag = true;
+    }
+    else {
+        sys.applySolution();
+        for (Line* line : lines) {
+            if (abs(*line->p1.x - *line->p2.x) < EPS && abs(*line->p1.y - *line->p2.y) < EPS && after_constraint) {
+                sys.undoSolution();
+                flag = true;
+                break;
+            }
+        }
+    }
+    
+    if (flag) {
+        QMessageBox::warning(this, QString("Error!"), QString("Last constraint is unavailable!"));
+            remove_constraint(constraints_count - 1);
+            constraints_count--;
+        }
+    after_constraint = false;
+    update();
+}
\ No newline at end of file
diff --git a/Canvas.h b/Canvas.h
index e3b9ba6..fc2bfb2 100644
--- a/Canvas.h
+++ b/Canvas.h
@@ -1,7 +1,5 @@
 #pragma once
-
-#define WIDGET_POSITION event->pos()
-#define UCS_POSITION screenToLogical(WIDGET_POSITION)
+constexpr auto EPS = 1e-9;
 
 #include <QWidget>
 #include <QMouseEvent>
@@ -30,7 +28,8 @@ enum class Mode : int
     Parallel = 2,     ///< Режим задания параллельности
     Coincedent = 3,   ///< Режим задания совпадения точек
     Horizontal = 4,   ///< Режим задания горизонтальности
-    Vertical = 5      ///< Режим задания вертикальности
+    Vertical = 5,      ///< Режим задания вертикальности
+    Perpendicular = 6
 };
 
 /// Удобный тип для хранения пары параллельных линий (порядок не важен)
@@ -94,10 +93,12 @@ private:
     /// Проверить, являются ли две линии уже параллельными (дубликат ограничения)
     bool areAlreadyParallel(Line* line1, Line* line2);
 
+    bool areAlreadyPerpendicular(Line* line1, Line* line2);
+
     // ====================== Методы работы с ограничениями ======================
 
     /// Удалить последние добавленные ограничения при ошибке солвера
-    void remove_constraints();
+    void remove_constraint(int);
 
     // ====================== Данные для перемещения объектов ======================
 
@@ -115,6 +116,7 @@ private:
     // ====================== Коллекции ограничений ======================
 
     std::set<LinePair> parallelPairs;   ///< Пары параллельных линий
+    std::set<LinePair> perpendicularPairs;
     std::set<PointPair> P2Ppairs;       ///< Пары совпадающих точек
     std::set<PointPair> HORIZ_pairs;    ///< Пары точек горизонтальных линий
     std::set<PointPair> VERT_pairs;     ///< Пары точек вертикальных линий
@@ -138,10 +140,12 @@ private:
 
     /// Структура для хранения информации о последнем добавленном ограничении
     /// (используется для отката при ошибке солвера)
-    struct LastConstraint {
-        Mode mode{ Mode::None };                     ///< Тип последнего ограничения
-        std::variant<LinePair, PointPair> data;      ///< Данные ограничения
-    };
 
-    LastConstraint lastConstraint;  ///< Информация о последнем добавленном ограничении
+    struct ConstraintInfo {
+        Mode mode;
+        std::variant<LinePair, PointPair> data;
+    };
+    std::map<int, ConstraintInfo> C_Info;
+
+    void solve_for_canvas();
 };
\ No newline at end of file
diff --git a/DRAWer_2_0.cpp b/DRAWer_2_0.cpp
index 4458cb3..1575b58 100644
--- a/DRAWer_2_0.cpp
+++ b/DRAWer_2_0.cpp
@@ -40,3 +40,9 @@ void DRAWer_2_0::on_Vertical_Button_clicked()
     ui.widget->changeMode(Mode::Vertical);
 }
 
+
+void DRAWer_2_0::on_Perpendicular_Button_clicked()
+{
+    ui.widget->changeMode(Mode::Perpendicular);
+}
+
diff --git a/DRAWer_2_0.h b/DRAWer_2_0.h
index 9d40eca..218e250 100644
--- a/DRAWer_2_0.h
+++ b/DRAWer_2_0.h
@@ -22,6 +22,8 @@ private slots:
 
     void on_Vertical_Button_clicked();
 
+    void on_Perpendicular_Button_clicked();
+
 private:
     Ui::DRAWer_2_0Class ui;
     int counter;
diff --git a/DRAWer_2_0.ui b/DRAWer_2_0.ui
index fe011c0..a906a54 100644
--- a/DRAWer_2_0.ui
+++ b/DRAWer_2_0.ui
@@ -52,6 +52,13 @@
         </property>
        </widget>
       </item>
+      <item>
+       <widget class="QPushButton" name="Perpendicular_Button">
+        <property name="text">
+         <string>Perpendicular</string>
+        </property>
+       </widget>
+      </item>
       <item>
        <widget class="QPushButton" name="P2P_Button">
         <property name="minimumSize">