diff --git a/src/main.cpp b/src/main.cpp
index 38751f0..cbbaf66 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -6,42 +6,69 @@
 #include <iostream>
 #include <cstring>
 #include <cstdlib>
+#include <vector>
+
+void plotCircle(std::vector<float> center, float radius, std::vector<float> color, float depth)
+{
+    constexpr int iter = 300;
+    constexpr float pi = 3.1415926535897f;
+    glColor3f(color.at(0), color.at(1), color.at(2));
+    for (int i = 0; i < iter; i++) {
+        float angle = i / (float)iter * pi * 2;
+        float angle_next = (i + 1) / (float)iter * pi * 2;
+        glVertex3f(center.at(0), center.at(1), depth);
+        glVertex3f(center.at(0) + radius * sinf(angle), center.at(1) + radius * cosf(angle), depth);
+        glVertex3f(center.at(0) + radius * sinf(angle_next), center.at(1) + radius * cosf(angle_next), depth);
+    }
+}
 
 static void render() {
     glBegin(GL_TRIANGLES);
-    glColor3f(1.0f, 0.0f, 0.0f);
-    glVertex3f(0.0f, 0.5f, 0.0f);
-    glColor3f(0.0f, 1.0f, 0.0f);
-    glVertex3f(-0.5f, -0.5f, 0.0f);
-    glColor3f(0.0f, 0.0f, 1.0f);
-    glVertex3f(0.5f, -0.5f, 0.0f);
+    constexpr int n = 300;
+    constexpr float pi = 3.1415926535897f;
+    float radius = 0.3f;
+    float inner_radius = 0.15f;
+    static int x = 0;
+    std::vector<float> green_color{.0f, 1.0f, .0f};
+    std::vector<float> red_color{1.0f, .0f, .0f};
+    std::vector<float> blue_color{ .0f, .0f, 1.0f };
+    std::vector<float> black_color{ .0f, .0f, 0.0f };
+    std::vector<float> green_circle_center{-0.4f, -0.4f, 1.0f};
+    std::vector<float> red_circle_center{0.0f, 0.4f, 1.0f};
+    std::vector<float> blue_circle_center{0.4f, -0.4f, 1.0f};
+    //Circles
+    plotCircle(green_circle_center, radius, green_color, 0.9f);
+    plotCircle(red_circle_center, radius, red_color, 0.9f);
+    for (int i = 0; i < n; i++) {
+        float angle = i / (float)n * pi * 2;
+        float angle_next = (i + 1) / (float)n * pi * 2;
+        if (angle > pi / 6 && angle < pi * 11 / 6)
+        {
+            glColor3f(0.0f, 0.0f, 1.0f);
+            glVertex3f(blue_circle_center.at(0), blue_circle_center.at(1), 0.5f);
+            glVertex3f(blue_circle_center.at(0) + radius * sinf(angle), blue_circle_center.at(1) + radius * cosf(angle), 0.5f);
+            glVertex3f(blue_circle_center.at(0) + radius * sinf(angle_next), blue_circle_center.at(1) + radius * cosf(angle_next), 0.5f);
+        }
+        else
+        {
+            continue;
+        }
+    }
+    plotCircle(green_circle_center, inner_radius, black_color, -0.1f);
+    plotCircle(red_circle_center, inner_radius, black_color, -0.1f);
+    plotCircle(blue_circle_center, inner_radius, black_color, -0.1f);
+    //Black Triangle
+    glColor3f(0.0f, 0.0f, 0.0f);
+    glVertex3f(green_circle_center.at(0), green_circle_center.at(1), 0.6f);
+    glVertex3f(red_circle_center.at(0), red_circle_center.at(1), 0.6f);
+    glVertex3f(blue_circle_center.at(0), blue_circle_center.at(1), 0.6f);
+
     CHECK_GL(glEnd());
-    /* glBegin(GL_TRIANGLES); */
-    /* constexpr int n = 100; */
-    /* constexpr float pi = 3.1415926535897f; */
-    /* float radius = 0.5f; */
-    /* float inner_radius = 0.25f; */
-    /* static int x = 0; */
-    /* x++; */
-    /* if (x > n) */
-    /*     x -= n; */
-    /* for (int i = 0; i < x; i++) { */
-    /*     float angle = i / (float)n * pi * 2; */
-    /*     float angle_next = (i + 1) / (float)n * pi * 2; */
-    /*     glVertex3f(0.0f, 0.0f, 0.0f); */
-    /*     glVertex3f(radius * sinf(angle), radius * cosf(angle), 0.0f); */
-    /*     glVertex3f(radius * sinf(angle_next), radius * cosf(angle_next), 0.0f); */
-        /* glVertex3f(inner_radius * sinf(angle), inner_radius * cosf(angle), 0.0f); */
-        /* glVertex3f(inner_radius * sinf(angle_next), inner_radius * cosf(angle_next), 0.0f); */
-        /* glVertex3f(inner_radius * sinf(angle), inner_radius * cosf(angle), 0.0f); */
-        /* glVertex3f(radius * sinf(angle_next), radius * cosf(angle_next), 0.0f); */
-    /* } */
-    /* CHECK_GL(glEnd()); */
 }
 
 int main() {
     if (!glfwInit()) {
-        const char *errmsg;
+        const char* errmsg;
         glfwGetError(&errmsg);
         if (!errmsg) errmsg = "(no error)";
         std::cerr << "failed to initialize GLFW: " << errmsg << '\n';
@@ -61,18 +88,20 @@ int main() {
     }
 
     // Create window
-    GLFWwindow *window = glfwCreateWindow(640, 640, "Example", NULL, NULL);
+    GLFWwindow* window = glfwCreateWindow(640, 640, "Example", NULL, NULL);
     if (!window) {
-        const char *errmsg;
+        const char* errmsg;
         glfwGetError(&errmsg);
         if (!errmsg) errmsg = "(no error)";
         std::cerr << "GLFW failed to create window: " << errmsg << '\n';
         std::cerr << "==============================================\n";
         if (!strcmp(errmsg, "X11: The DISPLAY environment variable is missing")) {
             std::cerr << "You seems not running with graphic display\n";
-        } else if (!strcmp(errmsg, "WGL: The driver does not appear to support OpenGL")) {
+        }
+        else if (!strcmp(errmsg, "WGL: The driver does not appear to support OpenGL")) {
             std::cerr << "Please consider install an OpenGL driver, or use the mesa driver\n";
-        } else if (!strcmp(errmsg, "WGL: Failed to create OpenGL context")) {
+        }
+        else if (!strcmp(errmsg, "WGL: Failed to create OpenGL context")) {
             std::cerr << "Your driver seems not supporting the required OpenGL version\n";
         }
         std::cerr << "- If you have a physical graphic card (e.g. NVIDIA), install it from your graphic card vendor official website: http://www.nvidia.com/Download/index.aspx\n";
@@ -103,11 +132,15 @@ int main() {
     CHECK_GL(glEnable(GL_BLEND));
     CHECK_GL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
     CHECK_GL(glPointSize(64.0f));
+    CHECK_GL(glEnable(GL_DEPTH_TEST));
+    CHECK_GL(glDepthMask(GL_TRUE));
 
     // start main game loop
     while (!glfwWindowShouldClose(window)) {
         // render graphics
         CHECK_GL(glClear(GL_COLOR_BUFFER_BIT));
+        CHECK_GL(glClearDepth(1.0f));
+        CHECK_GL(glClear(GL_DEPTH_BUFFER_BIT));
         render();
         // refresh screen
         glfwSwapBuffers(window);