29. Advancing levels

The basic changes needed to allow our game to advance levels should be quite simple: little more than a counter, so that we can know how many dots remain on screen.

Then, when we eat a dot we would decrease that counter, and when there are no dots remaining, we might call a new function to prepare the next level:

score += 10;
dots[i].visible = false;
remainingDots--;
if (remainingDots == 0)
    AdvanceLevel();
 

It its simplest from, that function might make all the dots visible again and take our player to its starting point. Also, we might increase the speed of our enemies, so that the second level is harder than the first one:

public static void AdvanceLevel()
{
    x = startX;
    y = startY;
 
    for (int i = 0; i < amountOfDots; i++)
        dots[i].visible = true;
 
    enemySpeed += 4;
}

We should be careful with that speed: our tile size is 32, so the speed of our enemies should be a divider of that number (such as 4, 8, 16 or 32), or otherwise they might get trapped in a certain point of the labyrinth and not to be able to exit towards the rest of the labyrinth.

The full source code might be:

/*
  First mini-graphics-game skeleton
  Version S: restarting a level
*/
 
using System;
 
public class SdlMuncher
{
    struct Dot
    {
        public int x;
        public int y;
        public bool visible;
    }
    static Dot[] dots;
    static int amountOfDots;
    static int remainingDots;
 
    struct Enemy
    {
        public float x;
        public float y;
        public float xSpeed;
        public float ySpeed;
    }
    static Enemy[] enemies;
    static int amountOfEnemies;
    static int enemySpeed;
 
    static bool sessionFinished = false;
    static int startX = 32 * 8;
    static int startY = 32 * 8;
    static int lives;
    static int x, y;
    static int pacSpeed;
 
    static Image dotImage;
    static Image enemyImage;
    static Image pacImage;
    static Image wallImage;
 
    static string[] map = {
            "-----------------",
            "-.......-.......-",
            "-.--.--.-.--.--.-",
            "-...............-",
            "-.--.-.---.-.--.-",
            "-....-..-..-....-",
            "----.--...--.----",
            ".................",
            "----.-.-.-.-.----",
            "-....-.-.-.-....-",
            "-.--.-.---.-.--.-",
            "-...............-",
            "-.--.-.---.-.--.-",
            "-....-.....-....-",
            "-----------------"
    };
    static int score;
    static Font sans18;
    static bool gameFinished;
    static Random randomGenerator;
 
 
    public static void Init()
    {
        bool fullScreen = false;
        SdlHardware.Init(800, 600, 24, fullScreen);
 
        dotImage = new Image("data/dot.png");
        enemyImage = new Image("data/ghostGreen.png");
        pacImage = new Image("data/pac01r.png");
        wallImage = new Image("data/wall.png");
 
        sans18 = new Font("data/Joystix.ttf", 18);
 
        // Data for the dots
        // First: count how many dots are there
        amountOfDots = 0;
        for (int row = 0; row < 15; row++)
        {
            for (int column = 0; column < 17; column++)
            {
                if (map[row][column] == '.')
                    amountOfDots++;
            }
        }
        dots = new Dot[amountOfDots];
 
        // Now, assign their coordinates
        int currentDot = 0;
        for (int row = 0; row < 15; row++)
        {
            for (int column = 0; column < 17; column++)
            {
                if (map[row][column] == '.')
                {
                    dots[currentDot].x = column * 32;
                    dots[currentDot].y = row * 32;
                    currentDot++;
                }
            }
        }
 
        // And enemies
        amountOfEnemies = 4;
        enemies = new Enemy[amountOfEnemies];
 
        randomGenerator = new Random();
    }
 
 
    public static void PrepareGameStart()
    {
        // Pac coordinates and speed
        x = startX;
        y = startY;
        pacSpeed = 4;
 
        // Coordinates for the enemies        
        enemySpeed = 4;
        enemies[0].x = 32; enemies[0].y = 1 * 32; enemies[0].xSpeed = enemySpeed;
        enemies[1].x = 32; enemies[1].y = 3 * 32; enemies[1].xSpeed = enemySpeed;
        enemies[2].x = 3 * 32; enemies[2].y = 9 * 32; enemies[2].xSpeed = -enemySpeed;
        enemies[3].x = 32; enemies[3].y = 11 * 32; enemies[3].xSpeed = enemySpeed;
 
        // All dots must be visible
        for (int i = 0; i < amountOfDots; i++)
            dots[i].visible = true;
        remainingDots = amountOfDots;
 
        // Resto of data for a new game
        score = 0;
        lives = 3;
    }
 
 
    public static void Intro()
    {
        int x = -40;
        bool exitIntro = false;
        do
        {
            SdlHardware.ClearScreen();
            SdlHardware.WriteHiddenText("Hit SPACE to start",
                300, 400,
                0xCC, 0xCC, 0xCC,
                sans18);
            SdlHardware.WriteHiddenText("or H for Help",
                330, 440,
                0xAA, 0xAA, 0xAA,
                sans18);
            SdlHardware.WriteHiddenText("or C for Credits",
                310, 480,
                0x88, 0x88, 0x88,
                sans18);
            SdlHardware.WriteHiddenText("or Q to Quit",
                340, 520,
                0x66, 0x66, 0x66,
                sans18);
 
            SdlHardware.DrawHiddenImage(enemyImage, x - 50, 300);
            SdlHardware.DrawHiddenImage(pacImage, x, 300);
            SdlHardware.ShowHiddenScreen();
            x += 8;
            if (x > 850) x = -40;
            SdlHardware.Pause(20);
            if (SdlHardware.KeyPressed(SdlHardware.KEY_C))
                ShowCredits();
            if (SdlHardware.KeyPressed(SdlHardware.KEY_H))
                ShowHelp();
            if (SdlHardware.KeyPressed(SdlHardware.KEY_SPC))
                exitIntro = true;
            if (SdlHardware.KeyPressed(SdlHardware.KEY_Q))
            {
                exitIntro = true;
                sessionFinished = true;
            }
        }
        while (!exitIntro);
    }
 
 
    public static void ShowCredits()
    {
        SdlHardware.ClearScreen();
        SdlHardware.WriteHiddenText("By DAM Ies San Vicente 2012-2013",
            200, 500,
            0xCC, 0xCC, 0xCC,
            sans18);
        SdlHardware.WriteHiddenText("Hit ESC to return",
            300, 540,
            0x99, 0x99, 0x99,
            sans18);
        SdlHardware.ShowHiddenScreen();
        do
        {
            SdlHardware.Pause(20);
        }
        while (!SdlHardware.KeyPressed(SdlHardware.KEY_ESC));
    }
 
 
    public static void ShowHelp()
    {
        SdlHardware.ClearScreen();
        SdlHardware.WriteHiddenText("Eat the dots, avoid the ghosts.",
            200, 500,
            0xCC, 0xCC, 0xCC,
            sans18);
        SdlHardware.WriteHiddenText("Hit ESC to return",
            300, 540,
            0x99, 0x99, 0x99,
            sans18);
        SdlHardware.ShowHiddenScreen();
        do
        {
            SdlHardware.Pause(20);
        }
        while (!SdlHardware.KeyPressed(SdlHardware.KEY_ESC));
    }
 
 
    public static bool CanMoveTo(int x, int y, string[] map)
    {
        bool canMove = true;
        for (int row = 0; row < 15; row++)
        {
            for (int column = 0; column < 17; column++)
            {
                if (map[row][column] == '-')
                    if ((x > column * 32 - 32) &&
                        (x < column * 32 + 32) &&
                        (y > row * 32 - 32) &&
                        (y < row * 32 + 32)
                        )
                    {
                        canMove = false;
                    }
            }
        }
        return canMove;
    }
 
 
    public static void DrawElements()
    {
        // Draw
        SdlHardware.ClearScreen();
        //Console.Write("Score: {0}",score);
 
        // Background map
        for (int row = 0; row < 15; row++)
        {
            for (int column = 0; column < 17; column++)
            {
                if (map[row][column] == '-')
                    SdlHardware.DrawHiddenImage(wallImage, column * 32, row * 32);
            }
        }
 
        for (int i = 0; i < amountOfDots; i++)
        {
            if (dots[i].visible)
                SdlHardware.DrawHiddenImage(dotImage, dots[i].x, dots[i].y);
        }
 
        SdlHardware.DrawHiddenImage(pacImage, x, y);
 
        for (int i = 0; i < amountOfEnemies; i++)
            SdlHardware.DrawHiddenImage(enemyImage,
                (int)enemies[i].x, (int)enemies[i].y);
 
        SdlHardware.WriteHiddenText("Score: " + score,
            610, 100,
            0x80, 0x80, 0xFF,
            sans18);
 
        SdlHardware.WriteHiddenText("Lives: " + lives,
            610, 140,
            0x80, 0x80, 0xFF,
            sans18);
 
        SdlHardware.ShowHiddenScreen();
    }
 
 
    public static void CheckInputDevices()
    {
        // Read keys and calculate new position
        if (SdlHardware.KeyPressed(SdlHardware.KEY_RIGHT)
                && CanMoveTo(x + pacSpeed, y, map))
            x += pacSpeed;
 
        if (SdlHardware.KeyPressed(SdlHardware.KEY_LEFT)
                && CanMoveTo(x - pacSpeed, y, map))
            x -= pacSpeed;
 
        if (SdlHardware.KeyPressed(SdlHardware.KEY_DOWN)
                && CanMoveTo(x, y + pacSpeed, map))
            y += pacSpeed;
 
        if (SdlHardware.KeyPressed(SdlHardware.KEY_UP)
                && CanMoveTo(x, y - pacSpeed, map))
            y -= pacSpeed;
 
        if (SdlHardware.KeyPressed(SdlHardware.KEY_ESC))
            gameFinished = true;
    }
 
 
    public static void MoveElements()
    {
        // Move enemies and environment
        for (int i = 0; i < amountOfEnemies; i++)
        {
            if (CanMoveTo((int)(enemies[i].x + enemies[i].xSpeed),
                    (int)(enemies[i].y + enemies[i].ySpeed), map))
            {
                enemies[i].x += enemies[i].xSpeed;
                enemies[i].y += enemies[i].ySpeed;
            }
            else
            {
                switch (randomGenerator.Next(0, 4))
                {
                    case 0: // Next move: to the right
                        enemies[i].xSpeed = enemySpeed;
                        enemies[i].ySpeed = 0;
                        break;
                    case 1: // Next move: to the left
                        enemies[i].xSpeed = -enemySpeed;
                        enemies[i].ySpeed = 0;
                        break;
                    case 2: // Next move: upwards
                        enemies[i].xSpeed = 0;
                        enemies[i].ySpeed = -enemySpeed;
                        break;
                    case 3: // Next move: downwards
                        enemies[i].xSpeed = 0;
                        enemies[i].ySpeed = enemySpeed;
                        break;
                }
            }
        }
    }
 
 
    public static void CheckCollisions()
    {
        // Collisions, lose energy or lives, etc
        for (int i = 0; i < amountOfDots; i++)
            if (dots[i].visible &&
                (x > dots[i].x - 32) &&
                (x < dots[i].x + 32) &&
                (y > dots[i].y - 32) &&
                (y < dots[i].y + 32)
                )
            {
                score += 10;
                dots[i].visible = false;
                remainingDots--;
                if (remainingDots == 0)
                    AdvanceLevel();
            }
 
        for (int i = 0; i < amountOfEnemies; i++)
            if (
                (x > enemies[i].x - 32) &&
                (x < enemies[i].x + 32) &&
                (y > enemies[i].y - 32) &&
                (y < enemies[i].y + 32)
                )
            {
                x = startX;
                y = startY;
                lives--;
                if (lives == 0)
                    gameFinished = true;
            }
    }
 
 
    public static void PauseTillNextFrame()
    {
        SdlHardware.Pause(40);
    }
 
 
    public static void AdvanceLevel()
    {
        x = startX;
        y = startY;
 
        for (int i = 0; i < amountOfDots; i++)
            dots[i].visible = true;
 
        enemySpeed += 4;
    }
 
 
    public static void Main()
    {
        Init();
        Intro();
 
        while (!sessionFinished)
        {
            PrepareGameStart();
 
            // Game Loop
            gameFinished = false;
            while (!gameFinished)
            {
                DrawElements();
                CheckInputDevices();
                MoveElements();
                CheckCollisions();
                PauseTillNextFrame();
            } // end of game loop
 
            Intro();
 
        } // end of session
    } // end of  Main
} // end of class