add base class for grid, update main and participant

main.py

@@ -1,12 +1,30 @@
 import sys
 
-from PyQt5.QtWidgets import QApplication
+from PyQt5.QtWidgets import QApplication, QStackedWidget
+
 
 from modules.participant import Participant
+from modules.grid import GridDots
+
+
+class MainWindow(QStackedWidget):
+    def __init__(self):
+        super().__init__()
+        self.participant_widget = Participant()
+        self.grid_widget = GridDots()
+        self.addWidget(self.participant_widget)
+        self.addWidget(self.grid_widget)
+
+        self.participant_widget.reg_success.connect(self.show_line_widget)
+
+    def show_line_widget(self):
+        """Method to show widget with index 1 in the stack"""
+        self.setCurrentIndex(1)  # change to lines not grid later
+
 
 if __name__ == '__main__':
     app = QApplication(sys.argv)
-    window = Participant()
+    window = MainWindow()
     window.setWindowTitle("3Dots")
     window.show()
     sys.exit(app.exec_())

modules/grid.py

@@ -0,0 +1,58 @@
+from PyQt5.QtGui import QPen, QBrush
+from PyQt5.QtCore import Qt, QPointF
+from PyQt5.QtWidgets import (
+    QWidget,
+    QGraphicsView,
+    QGraphicsScene,
+    QGraphicsEllipseItem,
+    QGraphicsLineItem,
+    QVBoxLayout
+)
+
+
+class GridDots(QWidget):
+    def __init__(self):
+        super().__init__()
+        self.view = QGraphicsView()
+        self.scene = QGraphicsScene()
+        self.scene.setSceneRect(0, 0, 800, 800)
+        self.view.setScene(self.scene)
+
+        self.dots = []
+        self.lines = set()
+        self.setup_ui()
+        self.create_grid()
+
+    def setup_ui(self):
+        layout = QVBoxLayout(self)
+        layout.addWidget(self.view)
+
+    def create_grid(self):
+        """Draw 3x3 grid of dots"""
+        dot_radius = 30
+        spacing = 240
+        offset = 150
+
+        for row in range(3):
+            for col in range(3):
+                x, y, = offset + col * spacing, offset + row * spacing
+                dot = QGraphicsEllipseItem(
+                    x - dot_radius, y - dot_radius,
+                    2 * dot_radius, 2 * dot_radius)
+                dot.setBrush(QBrush(Qt.black))
+                self.scene.addItem(dot)
+                self.dots.append((x, y))
+
+    def draw_line(self, start, end):
+        line_id = tuple(sorted((start, end)))
+        if line_id not in self.lines:
+            start_pos = QPointF(*self.dots[start])
+            end_pos = QPointF(*self.dots[end])
+
+            line = QGraphicsLineItem(
+                start_pos.x(), start_pos.y(),
+                end_pos.x(), end_pos.y())
+
+            line.setPen(QPen(Qt.black, 2))
+            self.scene.addItem(line)
+            self.lines.add(line_id)

modules/participant.py

@@ -1,3 +1,4 @@
+from PyQt5.QtCore import Qt, pyqtSignal
 from PyQt5.QtWidgets import (
     QWidget,
     QVBoxLayout,
@@ -13,10 +14,10 @@ from PyQt5.QtWidgets import (
     QSpinBox
 )
 
-from PyQt5.QtCore import Qt
-
 
 class Participant(QWidget):
+    reg_success = pyqtSignal()
+
     def __init__(self):
         super().__init__()
 
@@ -79,5 +80,11 @@ class Participant(QWidget):
             QMessageBox.warning(
                 self, 'Input Error', 'Please select your sex.')
         else:
-            QMessageBox.information(
+            result = QMessageBox.information(
-                self, 'Success', f'Participant Registered: {identifier}, Age: {age}, Sex: {sex}')
+                self,
+                'Success',
+                f'Participant Registered: {identifier}, Age: {age}, Sex: {sex}'
+                )
+
+            if result == QMessageBox.Ok:
+                self.reg_success.emit()