Game Over condition simple Snake c++ game

Question

I have basic knowledge of c++ and am trying to create a simple Snake game that runs in a while loop, as long as a "Game Over" condition evaluates to false. If it turns to "true" (when the snakes head goes out of bounds), "Game Over!" is printed on a lcd screen.

For some reason, the code skips directly to the game over screen without running the game itself.

My code involves a few classes, and in one of those I have a collision detection function that looks like this:

bool SnakeEngine::collision_detection()
{
    // check the snake coordinates so that the head doesn't go off screen
    if (_head_y < 1) {
        return 1;
    }
    if (_head_y > HEIGHT - 4) {
        return 1;
    }
    if (_head_x < 1) {
        return 1;
    }
    if (_head_x > WIDTH - 4) {
        return 1;
    } else {
        return 0;
    }

}

And in the main loop I have:

int main()
{
    snake.draw(lcd); // draw the initial game frame and the sprites
    lcd.refresh();

    while(!snake.collision_detection()) {

        snake.read_input(pad); // reads the user input
        snake.update(pad); // updates the sprites positions and calls the collision_detection() function
        render(); // clears the lcd, draws the sprites in the updated positions, refreshes the lcd
        wait(1.0f/fps);

    }
    lcd.printString("Game Over!",6,4);
    lcd.refresh();
}

How come is this not working? Thank you

It sounds like you may need to learn how to use a debugger to step through your code. With a good debugger, you can execute your program line by line and see where it is deviating from what you expect. This is an essential tool if you are going to do any programming. Further reading: [How to debug small programs](http://ericlippert.com/2014/03/05/how-to-debug-small-programs/) — Nick, Apr 03 '18 at 14:42
My money would be on missing initialization of `_head_x` or `_head_y`, or initializing them to 0. But - you should learn to use a debugger. — einpoklum, Apr 03 '18 at 14:44
FYI, see [What are the rules about using an underscore in a C++ identifier?](https://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier) — Thomas Matthews, Apr 03 '18 at 15:25

score 1 · Answer 1 · answered Apr 03 '18 at 15:29

The collision detection is a suspect. If all specific conditions which you check do not return true (1) the final result should be false (0).

This condition is too restrictive:

  if (_head_x > WIDTH - 4) {
        return 1;
    } else {
        return 0;
    }

It should be limited to:

  if (_head_x > WIDTH - 4) {
        return 1;
  }

  return 0;

The modified code with the use of bool types true and false looks like:

bool SnakeEngine::collision_detection()
{
    // check the snake coordinates so that the head doesn't go off screen
    if (_head_y < 1) {
        return true;
    }

    if (_head_y > HEIGHT - 4) {
        return true;
    }

    if (_head_x < 1) {
        return true;
    }

    if (_head_x > WIDTH - 4) {
        return true;
    } 

    return false;
}

seccpur · Accepted Answer · 2018-04-03T15:09:42.357

Try this, just guessing.I think when all the four conditions are false, than you should conclude that there is no collision. I think you did a blunder in the last else statement in your collision_detection() .

bool SnakeEngine::collision_detection()
{
    // check the snake coordinates so that the head doesn't go off screen
    if (  _head_y < 1 || _head_y > (HEIGHT - 4) || _head_x < 1 || _head_x > (WIDTH - 4) )
        return true;

       return false;
}

Game Over condition simple Snake c++ game

2 Answers2