fix issue with block placement

module/block.py

@@ -52,3 +52,13 @@ class AirBlock(Block):
 
     def __init__(self, x: int, y: int):
         super().__init__(x, y)
+
+
+class WaterBlock(Block):
+    id = 'water'
+    color = COLORS.get(id)
+    flowable = True
+    collision = False
+
+    def __init__(self, x: int, y: int):
+        super().__init__(x, y)

module/player.py

@@ -1,4 +1,5 @@
 from module import WIDTH, HEIGHT, JUMP_FORCE
+from module.block import AirBlock
 
 
 # 玩家类
@@ -8,7 +9,7 @@ class Player:
         self.y = HEIGHT // 2
         self.velocity = 0
         self.on_ground = False
-        self.selected_block = "grass"
+        self.selected_block = AirBlock
 
     def move(self, dx, dy):
         new_x = self.x + dx