# Sprite Rotation Around a Point¶

This non-interactive example demonstrates two applications of rotating a sprite around a point:

1. On the left, a beam spinning around a point in a circle

2. On the right, a platform rotating around a point while staying flat

Although this behavior is inspired by platformers, it could be useful for other types of games.

The base class used in this example offers circular movement with finer control than the one in Collect Coins that are Moving in a Circle.

For a related example demonstrating how to mix rotation around a point with user input, see Move By Keyboard, Fire Towards Mouse.

sprite_rotate_around_point.py
```  1"""
2Rotating Sprites Around Points
3
4Two minimal examples demonstrating how to rotate sprites around points
5and how you might apply them in a game.
6
7Artwork from https://kenney.nl
8
9If Python and Arcade are installed, this example can be run from the command line with:
11"""
14
15SCREEN_WIDTH = 800
16SCREEN_HEIGHT = 600
17QUARTER_WIDTH = SCREEN_WIDTH // 4
18HALF_HEIGHT = SCREEN_HEIGHT // 2
19
20
21SCREEN_TITLE = "Rotating Sprites Around Points"
22
23
25    """
26    This sprite subclass implements a generic rotate_around_point method.
27    """
28
29    def rotate_around_point(self, point, degrees, change_angle=True):
30        """
31        Rotate the sprite around a point by the set amount of degrees
32
33        You could remove the change_angle keyword and/or angle change
34        if you know that sprites will always or never change angle.
35
36        :param point: The point that the sprite will rotate about
37        :param degrees: How many degrees to rotate the sprite
38        :param change_angle: Whether the sprite's angle should also be adjusted.
39        """
40
41        # If change_angle is true, change the sprite's angle
42        if change_angle:
43            self.angle += degrees
44
45        # Move the sprite along a circle centered on the point by degrees
46        self.position = rotate_point(
47            self.center_x, self.center_y,
48            point[0], point[1], degrees)
49
50
52
53    def __init__(self):
54        super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
55
57
58        # This example is based off spinning lines of fire from Mario games
60        self.left_rotating_laser_sprite = RotatingSprite(
61            ":resources:images/space_shooter/laserBlue01.png",
62            center_x=QUARTER_WIDTH + 26, center_y=HALF_HEIGHT)
63
65            ":resources:images/tiles/boxCrate.png", scale=0.25,
66            center_x=QUARTER_WIDTH, center_y=HALF_HEIGHT)
67
69            "change_angle = True",
70            QUARTER_WIDTH, SCREEN_HEIGHT // 2 - 150,
71            anchor_x='center')
72
73        # This example demonstrates how to make platforms rotate around a point
74        self.right_rotating_platform_sprite = RotatingSprite(
75            ":resources:images/tiles/grassHalf.png", scale=0.25,
76            center_x=3 * QUARTER_WIDTH + 50, center_y=HALF_HEIGHT)
77
79            ":resources:images/tiles/boxCrate.png", scale=0.25,
80            center_x=3 * QUARTER_WIDTH, center_y=HALF_HEIGHT)
81
83            "change_angle = False",
84            3 * QUARTER_WIDTH, HALF_HEIGHT - 150,
85            anchor_x='center')
86
87        self.sprites.extend([
88            self.laser_base_sprite,
89            self.left_rotating_laser_sprite,
90            self.platform_base_sprite,
91            self.right_rotating_platform_sprite])
92
93    def on_update(self, delta_time: float):
94        # Rotate the laser sprite and change its angle
95        self.left_rotating_laser_sprite.rotate_around_point(
96            self.laser_base_sprite.position,
97            120 * delta_time)
98
99        # Rotate the platform sprite but don't change its angle
100        self.right_rotating_platform_sprite.rotate_around_point(
101            self.platform_base_sprite.position,
102            60 * delta_time, False)
103
104    def on_draw(self):
105        # Draw the sprite list.
106        self.clear()
107        self.sprites.draw()
108
109        self.laser_text.draw()
110        self.platform_text.draw()
111
112
113def main():
114    window = ExampleWindow()
115    window.run()
116
117
118if __name__ == '__main__':
119    main()
```