シューティングゲームにおける弾の実装について

前提・実現したいこと

シューティングゲームで、円上を動く自機から垂直方向にまっすぐに発射される弾を作りたいのですが、自機の円の中心からの回転角度を利用して記述しているため、弾をうったあと、機体が動くと同時に弾をまっすぐとぶのではなく、回転してしまいます。どのように解消すればいいのか教えてほしいです。

発生している問題・エラーメッセージ

該当のソースコード

python
1import pygame
2import sys
3import math
4import random
5
6img_galaxy = pygame.image.load("galaxy.png")
7img_ship = [
8    pygame.image.load("starship1.png"),
9    pygame.image.load("starship_l1.png"),
10    pygame.image.load("starship_r1.png"),
11    pygame.image.load("starship_burner.png")
12]
13img_weapon = pygame.image.load("bullet.png")
14img_center = pygame.image.load("center.png")
15img_enemy = [
16    pygame.image.load("enemy0.png"),
17    pygame.image.load("enemy1.png")
18]
19tmr = 0
20r = 0
21s_x = 0
22s_y = 0
23s_d = 0
24key_spc = 0
25
26msl_f = False
27msl_x = 0
28msl_y = 0
29
30MISSILE_MAX = 200
31msl_no = 0
32msl_f = [False]*MISSILE_MAX
33msl_x = [0]*MISSILE_MAX
34msl_y = [0]*MISSILE_MAX
35
36ENEMY_MAX = 100
37emy_no = 0
38emy_f = [False]*ENEMY_MAX
39emy_x = [0]*ENEMY_MAX
40emy_y = [0]*ENEMY_MAX
41emy_a = [0]*ENEMY_MAX
42emy_type = [0]*ENEMY_MAX
43emy_speed = [0]*ENEMY_MAX
44
45EMY_BULLET = 0
46LINE_T = -80
47LINE_B = 800
48LINE_L = -80
49LINE_R = 1040
50
51zx =0
52zy =0
53
54def center(scrn):
55    scrn.blit(img_center,[380,260])
56
57def get_dis(x1,x2,y1,y2):
58    return ((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))
59
60def move_starship(scrn,key):
61    global s_x,s_y,s_d,key_spc,r
62    s_d = 0
63    if key[pygame.K_LEFT] == 1:
64        s_d = 1
65        r = r - 8
66    if key[pygame.K_RIGHT] == 1:
67        s_d = 2
68        r = r + 8
69    key_spc = (key_spc+1)*key[pygame.K_SPACE]
70    if key_spc%5 ==1:
71        set_missile()
72
73    img_rz = pygame.transform.rotate(img_ship[s_d],-1*r)
74
75    s_x = 120*math.cos(math.radians(r-90))+480-25-5
76    s_y = 120*math.sin(math.radians(r-90))+360-25-5
77
78    scrn.blit(img_rz,[s_x,s_y])
79
80def set_missile():
81    global msl_no,r,s_x,s_y,zx,zy
82    msl_f[msl_no] = True
83    msl_x[msl_no] = (120+25)*math.cos(math.radians(r-90))+480-25-5
84    msl_y[msl_no] = (120+25)*math.sin(math.radians(r-90))+360-25-5
85    zx = msl_x[msl_no]-s_x
86    zy = msl_y[msl_no]-s_y
87
88    msl_no = (msl_no+1)%MISSILE_MAX
89
90def move_missiele(scrn):
91    global r,zx,zy
92    for i in range(MISSILE_MAX):
93        if msl_f[i] == True:
94            msl_x[i] = msl_x[i] + zx
95            msl_y[i] = msl_y[i] + zy
96            img_r = pygame.transform.rotate(img_weapon, -1 * r)
97            scrn.blit(img_r,[msl_x[i]-10,msl_y[i]-32])
98        if msl_y[i]<0:
99            msl_f[i] = False
100
101def bring_enemy():
102    if tmr%30 == 0:
103        set_enemy(random.randint(20,940),LINE_T,90,1,6)
104
105def set_enemy(x,y,a,ty,sp):
106    global emy_no
107    while True:
108        if emy_f[emy_no] ==False:
109            emy_f[emy_no] = True
110            emy_x[emy_no] = x
111            emy_y[emy_no] = y
112            emy_a[emy_no] = a
113            emy_type[emy_no] = ty
114            emy_speed[emy_no] = sp
115            break
116        emy_no = (emy_no+1)%ENEMY_MAX
117
118def move_enemy(scrn): # 敵機の移動
119    for i in range(ENEMY_MAX):
120        if emy_f[i] == True:
121            ang = -90-emy_a[i]
122            png = emy_type[i]
123            emy_x[i] = emy_x[i] + emy_speed[i]*math.cos(math.radians(emy_a[i]))
124            emy_y[i] = emy_y[i] + emy_speed[i]*math.sin(math.radians(emy_a[i]))
125            if emy_type[i] == 1 and emy_y[i] > 360:
126                set_enemy(emy_x[i], emy_y[i], 90, 0, 8)
127                emy_a[i] = -45
128                emy_speed[i] = 16
129            if emy_x[i] < LINE_L or LINE_R < emy_x[i] or emy_y[i] < LINE_T or LINE_B < emy_y[i]:
130                emy_f[i] = False
131            if emy_type[i] != EMY_BULLET:
132                for n in range(MISSILE_MAX):
133                    if msl_f[n]== True and math.dist((emy_x[i],emy_y[i]),(msl_x[n],msl_y[n]))< 7+25:
134                        msl_f[n] = False
135                        emy_f[i] = False
136            img_rz = pygame.transform.rotozoom(img_enemy[png], ang, 1.0)
137            scrn.blit(img_rz, [emy_x[i]-img_rz.get_width()/2, emy_y[i]-img_rz.get_height()/2])
138
139def main():
140    global tmr
141    pygame.init()
142    pygame.display.set_caption("地球防衛軍")
143    screen = pygame.display.set_mode((960,720))
144    clock = pygame.time.Clock()
145    while True:
146        tmr = tmr + 1
147        for event in pygame.event.get():
148            if event.type == pygame.QUIT:
149                pygame.quit()
150                sys.exit()
151            if event.type == pygame.KEYDOWN:
152                if event.key == pygame.K_F1:
153                    screen = pygame.display.set_mode((960,720),pygame.FULLSCREEN)
154                if event.key == pygame.K_F2 or event.key == pygame.K_ESCAPE:
155                    screen = pygame.display.set_mode((960,720))
156        screen.blit(img_galaxy,[0,0])
157        center(screen)
158
159        key = pygame.key.get_pressed()
160        move_starship(screen,key)
161        move_missiele(screen)
162        bring_enemy()
163        move_enemy(screen)
164
165        pygame.display.update()
166        clock.tick(30)
167
168if __name__ == '__main__':
169    main()