Почему программа ведет себя странно?

#include <windows.h>
#include <vector>
//#include <typeinfo.h>
#include <iterator>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <stdio.h>
#include <iostream>
#include <math.h>


using namespace std;

bool side = true;
GLFWwindow* window = 0;


void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
{
    // Когда пользователь нажимает ESC, мы устанавливаем свойство WindowShouldClose в true,
    // и приложение после этого закроется
    if(key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
}

int main() {
    if (!glfwInit()) {
      fprintf(stderr, "ERROR: could not start GLFW3\n");
      return 1;
    }

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    window = glfwCreateWindow(640, 480, "first", 0, 0);
    if (window == 0)
    {
        //std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glewExperimental = GL_TRUE;
    glewInit();

    const GLubyte* renderer = glGetString(GL_RENDERER); // get renderer string
    const GLubyte* version = glGetString(GL_VERSION); // version as a string
    printf("Renderer: %s\n", renderer);
    printf("OpenGL version supported %s\n", version);
    glEnable(GL_DEPTH_TEST); // enable depth-testing
    glDepthFunc(GL_LESS); // depth-testing interprets a smaller value as "closer"


    int width, height;
    glfwGetFramebufferSize(window, &width, &height);
    glViewport(0, 0, width, height);

    GLfloat ourColor[] = {0.2f, 0.3f, 0.6f, 1.0f};

    const GLchar* const vertexSource =
            "#version 400\n"
            "in vec3 position;"
            "void main(){"
            "gl_Position = vec4(position.x, position.y, position.z, 1.0);}\0";

    const GLchar* const fragmentSource =
            "#version 330 core\n"
            "uniform vec4 ourColor;"
            "out vec4 color;"
            "void main(){"
            "color = ourColor;}\0";

    GLuint vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexSource, NULL);
    glCompileShader(vertexShader);
    GLint success;
    GLchar infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;

    }else{
        cout << "Success init vertex shader\n";
    }
    GLuint fragmentShader;
    vertexShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
    glCompileShader(fragmentShader);
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;

    }else{
        cout << "Success init fragment shader\n";
    }



    GLuint shaderProgram;
    shaderProgram = glCreateProgram();

    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if(!success)
    {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;

    }else{
        cout << "Success link shader's program\n";
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);


    GLfloat vertexTriangle[] = {
      -0.5f, -0.5f, 0.0f, //левый нижний
       0.5f, -0.5f, 0.0f, //правый нижний
       0.0f,  0.5f, 0.0f  //верхний
    };

    GLuint VBO, VAO;
    glGenBuffers(1, &VBO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), vertexTriangle, GL_DYNAMIC_DRAW);

    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);

    bool sideY = true;
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

    while(!glfwWindowShouldClose(window))
    {
        sideY++;

        GLuint VBO, VAO;
        glGenBuffers(1, &VBO);

        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), vertexTriangle, GL_DYNAMIC_DRAW);

        glGenVertexArrays(1, &VAO);
        glBindVertexArray(VAO);

        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        GLfloat timeValue = glfwGetTime();
        GLfloat greenValue = (sin(timeValue) / 2) + 0.5;
        GLint vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
        glUseProgram(shaderProgram);
        glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glfwPollEvents();
        glfwSwapBuffers(window);

    }

    glfwTerminate();
    return 0;
}