diff --git a/src/DrawingTools.java b/src/DrawingTools.java
index 398905a..00f5e74 100644
--- a/src/DrawingTools.java
+++ b/src/DrawingTools.java
@@ -5,6 +5,8 @@ import ch.aplu.turtle.Turtle;
  */
 public class DrawingTools {
     public static void drawSquare(Turtle turtle, double size) {
+        int width = (int) size / 10;
+        turtle.penWidth(width);
         for (int i = 0; i < 4; i++) {
             turtle.forward(size).left(90);
         }