Fireballs

Now it is time for some serious action. You will add a fireball that moves back and forth in the dungeon. This is by far the most complex feature so far, but it can be done in small steps. Also, you have already created a lot of code that should help. The following steps are necessary:

1. create a Fireball class

2. add a fireball to the level

3. draw the fireball

4. move the fireball

5. slow down the fireball

6. make the fireball cause damage

Create a Fireball class

You need a new class, so that the fireball can move independently. Also, this makes it possible to add many fireballs.

Create a new class Fireball with the following attributes:

• a x position

• a y position

• a direction indicating where the fireball will move, e.g. "up"

You can borrow examples from the other classes.

Add a fireball to the level

The game needs to store the fireballs as an extra list. Add a new attribute to the DungeonGame class that is a list of fireball objects. You can borrow the strategy from the Teleporter class, the code should be very similar.

• Also, create a fireball when the level is created.

• Create a single fireball first.

• Decide on a starting position and a direction.

Hint

The game should run without any visible changes at this point.

Draw the fireball

The drawing is not that different either. Copy the section in draw() that draws teleporters and draw fireball.png instead.

Hint

Now you should see a fireball that does not move.

Move the fireball

The logic to move a fireball is as follows:

• calculate the position where the fireball would move

• if that square is free, move there

• if not, turn around

Implement these steps in a new function move_fireball():

def move_fireball(game, fireball):
    new_x, new_y = get_next_position(fireball.x, fireball.y, fireball.direction)
    if game.level[new_y][new_x] in ".€k":  # flies over coins and keys
        fireball.x = new_x
        fireball.y = new_y

You also need to take care of the situation when the fireball hits an obstacle. In that case, reverse the direction:

elif fireball.direction == "right":
    fireball.direction = "left"
..

Add the code for other direction changes you would like to have.

Check if the program is running although nothing is moving yet.

Regular updates

The fireballs need to be moved regularly. Add a new function update() to game.py that moves all the fireballs:

def update(game):
    for f in game.fireballs:
        move_fireball(game, f)

Import and call the update function in main.py in the while loop after drawing:

from game import update

while game.status == "running":
    draw(game, images, moves)
    update(game)

Run the game. Now you should see a fireball moving.

Slow down the fireball

Depending on your machine, the fireball is either very fast or insanely, abysmally fast. For any human player to have a chance dodging it, you need to make the movement slower.

The smooth movement mechanism will help with that. If you make sure that the new movement does not start before an old one finishes, the speed should become manageable.

First, the fireball needs to remember its move to check if it is finished. Add to the Fireball class:

class Fireball:
    ...
    move: Move = None

Now, create smooth moves in the move_fireball() function. They need to be added to both the fireball and the game:

def move_fireball(game, fireball):
    ...
    fireball.move = Move(
        tile="fireball",
        from_x=fireball.x, from_y=fireball.y,
        speed_x = ..., speed_y = ...
    )
    game.moves.append(fireball.move)

Hint

Figuring out the right values for speed_x and speed_y can be tricky. It either requires a lot of if commands. An easier alternative is to calculate it from the old and new x position!

Now the trick is to only update the fireballs if they have completed their move. Modify the update() function:

def update(game):
    for f in game.fireballs:
        if f.move and f.move.complete:
            move_fireball(game, f)

Now the fireball should move smoothly and in an acceptable speed!

Make the fireball cause damage

It is great to watch your fireballs fly around. However, they are not very dangerous. Let’s make them more harmful.

Add a collision check, comparing the position of the player to that of each fireball. Complete the code:

def check_collision(game):
    for f in game.fireballs:
        if f.x == game.x and ...:
            take_damage()

Then add a call to the check_collision() function at the end of the update() function. This takes care of fireballs moving into the player.

Add another call to check_collision() to the move_player() function, so that it also hurts when the player moves into a fireball.