refactor: move literals into constant variables

main.py

@@ -1,20 +1,36 @@
 import pygame
 
+WIN_WIDTH = 800
+WIN_HEIGHT = 600
+WIN_ICON = "img/tetris_icon.png"
+WIN_TITLE = "Tetris"
+WIN_BG_COLOR = (100, 149, 237) # cornflower blue, RGB
+
+def draw(screen):
+    # draw window bg
+    screen.fill(WIN_BG_COLOR)
+
+    pygame.display.update()
+
 def main():
     pygame.init()
 
-    screen = pygame.display.set_mode((800, 600))
-    pygame.display.set_caption("Tetris")
-    icon = pygame.image.load("img/tetris_icon.png")
-    pygame.display.set_icon(icon)
+    screen = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))
+    loaded_icon = pygame.image.load(WIN_ICON)
+
+    pygame.display.set_caption(WIN_TITLE)
+    pygame.display.set_icon(loaded_icon)
 
     is_running = True
     while is_running:
         for event in pygame.event.get():
+
             if event.type == pygame.QUIT:
                 is_running = False
+        
+        draw(screen)
 
-        screen.fill((100, 149, 237))
-        pygame.display.update()
+    pygame.quit()
 
-main()
+# start main function
+main()