diff --git a/u02/include/star_tool.h b/u02/include/star_tool.h
index 2f60bbb..eb1160f 100644
--- a/u02/include/star_tool.h
+++ b/u02/include/star_tool.h
@@ -26,7 +26,10 @@ std::vector<std::pair<float, float>> star(int n, float r1, float r2, int x = 0,
 
 class star_tool : public tool_base {
 public:
-  star_tool(canvas_buffer &canvas);
+  // Initialize a new star tool.
+  // It can draw stars with arbitrary number of spikes (however, at least 2).
+  // The preview is hard coded to 5 spikes.
+  star_tool(canvas_buffer &canvas, int spikes = 5);
 
   void draw(int x0, int y0, int x1, int y1);
 
@@ -37,6 +40,6 @@ public:
   void set_radius_factor(int radius_factor);
 
 private:
-  int spikes = 5;
+  int spikes;
   float radius_factor = 1.0 / 3.0;
 };
diff --git a/u02/src/star_tool.cpp b/u02/src/star_tool.cpp
index 1e6b19f..fb9bd72 100644
--- a/u02/src/star_tool.cpp
+++ b/u02/src/star_tool.cpp
@@ -41,8 +41,9 @@ std::vector<std::pair<float, float>> star(int n, float r1, float r2, int x,
       base_angle);
 }
 
-star_tool::star_tool(canvas_buffer &canvas) : tool_base(canvas) {
+star_tool::star_tool(canvas_buffer &canvas, int spikes) : tool_base(canvas) {
   shape = TS_STAR;
+  set_spikes(spikes);
 }
 
 void star_tool::draw(int x0, int y0, int x1, int y1) {