Sprites That Follow The Player 2¶

sprite_follow_simple_2.py
```  1"""
3
4This calculates a 'vector' towards the player and randomly updates it based
5on the player's location. This is a bit more complex, but more interesting
6way of following the player.
7
8Artwork from http://kenney.nl
9
10If Python and Arcade are installed, this example can be run from the command line with:
12"""
13
14import random
16import math
17import os
18
19# --- Constants ---
20SPRITE_SCALING_PLAYER = 0.5
21SPRITE_SCALING_COIN = 0.2
22COIN_COUNT = 5
23COIN_SPEED = 0.5
24
25SCREEN_WIDTH = 800
26SCREEN_HEIGHT = 600
27SCREEN_TITLE = "Sprite Follow Player Simple Example 2"
28
29SPRITE_SPEED = 0.5
30
31
33    """
34    This class represents the coins on our screen. It is a child class of
35    the arcade library's "Sprite" class.
36    """
37
38    def follow_sprite(self, player_sprite):
39        """
40        This function will move the current sprite towards whatever
41        other sprite is specified as a parameter.
42
43        We use the 'min' function here to get the sprite to line up with
44        the target sprite, and not jump around if the sprite is not off
45        an exact multiple of SPRITE_SPEED.
46        """
47
48        self.center_x += self.change_x
49        self.center_y += self.change_y
50
51        # Random 1 in 100 chance that we'll change from our old direction and
52        # then re-aim toward the player
53        if random.randrange(100) == 0:
54            start_x = self.center_x
55            start_y = self.center_y
56
57            # Get the destination location for the bullet
58            dest_x = player_sprite.center_x
59            dest_y = player_sprite.center_y
60
61            # Do math to calculate how to get the bullet to the destination.
62            # Calculation the angle in radians between the start points
63            # and end points. This is the angle the bullet will travel.
64            x_diff = dest_x - start_x
65            y_diff = dest_y - start_y
66            angle = math.atan2(y_diff, x_diff)
67
68            # Taking into account the angle, calculate our change_x
69            # and change_y. Velocity is how fast the bullet travels.
70            self.change_x = math.cos(angle) * COIN_SPEED
71            self.change_y = math.sin(angle) * COIN_SPEED
72
73
75    """ Our custom Window Class"""
76
77    def __init__(self):
78        """ Initializer """
79        # Call the parent class initializer
80        super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
81
82        # Set the working directory (where we expect to find files) to the same
83        # directory this .py file is in. You can leave this out of your own
84        # code, but it is needed to easily run the examples using "python -m"
85        # as mentioned at the top of this program.
86        file_path = os.path.dirname(os.path.abspath(__file__))
87        os.chdir(file_path)
88
89        # Variables that will hold sprite lists
90        self.player_list = None
91        self.coin_list = None
92
93        # Set up the player info
94        self.player_sprite = None
95        self.score = 0
96
97        # Don't show the mouse cursor
98        self.set_mouse_visible(False)
99
101
102    def setup(self):
103        """ Set up the game and initialize the variables. """
104
105        # Sprite lists
108
109        # Score
110        self.score = 0
111
112        # Set up the player
113        # Character image from kenney.nl
115        self.player_sprite.center_x = 50
116        self.player_sprite.center_y = 50
117        self.player_list.append(self.player_sprite)
118
119        # Create the coins
120        for i in range(COIN_COUNT):
121            # Create the coin instance
122            # Coin image from kenney.nl
123            coin = Coin(":resources:images/items/coinGold.png", SPRITE_SCALING_COIN)
124
125            # Position the coin
126            coin.center_x = random.randrange(SCREEN_WIDTH)
127            coin.center_y = random.randrange(SCREEN_HEIGHT)
128
129            # Add the coin to the lists
130            self.coin_list.append(coin)
131
132    def on_draw(self):
133        """ Draw everything """
135        self.coin_list.draw()
136        self.player_list.draw()
137
138        # Put the text on the screen.
139        output = f"Score: {self.score}"
141
142    def on_mouse_motion(self, x, y, dx, dy):
143        """ Handle Mouse Motion """
144
145        # Move the center of the player sprite to match the mouse x, y
146        self.player_sprite.center_x = x
147        self.player_sprite.center_y = y
148
149    def on_update(self, delta_time):
150        """ Movement and game logic """
151
152        for coin in self.coin_list:
153            coin.follow_sprite(self.player_sprite)
154
155        # Generate a list of all sprites that collided with the player.
157
158        # Loop through each colliding sprite, remove it, and add to the score.
159        for coin in hit_list:
160            coin.kill()
161            self.score += 1
162
163
164def main():
165    """ Main method """
166    window = MyGame()
167    window.setup()