I want to move camera with keyboard in OpenGL. I followed the LearnOpenGL Camera tutorial, but I have no idea how can I use them.

Here is my code:

```
#define GL_GLEXT_PROTOTYPES
#include <stdlib.h>
#include <GLFW/glfw3.h>
#include <GL/gl.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
GLFWwindow *window;
void startGame()
{
float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void * )0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
float cameraSpeed = 0.05f;
glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 3.0f);
glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);
glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);
glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp);
if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
{
cameraPos += cameraSpeed * cameraFront;
}
if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
{
cameraPos -= glm::normalize(glm::cross(cameraFront, cameraUp)) * cameraSpeed;
}
if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
{
cameraPos -= cameraSpeed * cameraFront;
}
if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
{
cameraPos += glm::normalize(glm::cross(cameraFront, cameraUp)) * cameraSpeed;
}
glUniformMatrix4fv(glGetUniformLocation(0, "view"), 1, GL_FALSE, &view[0][0]);
}
int main(int argc, char **argv)
{
if (!glfwInit())
{
exit(EXIT_FAILURE);
}
GLFWmonitor *monitor = glfwGetPrimaryMonitor();
const GLFWvidmode *mode = glfwGetVideoMode(monitor);
glfwWindowHint(GLFW_RED_BITS, mode->redBits);
glfwWindowHint(GLFW_GREEN_BITS, mode->greenBits);
glfwWindowHint(GLFW_BLUE_BITS, mode->blueBits);
glfwWindowHint(GLFW_REFRESH_RATE, mode->refreshRate);
window = glfwCreateWindow(mode->width, mode->height, "KGCraft", monitor, NULL);
glfwMakeContextCurrent(window);
while (!glfwWindowShouldClose(window))
{
startGame();
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
}
```