I'm building a game in Pygame that involves moving a red rectangle (player) using the arrow keys. I've gotten the player to move with the arrow keys (arrow keys control velocity, enter key confirms the move), but I need to be able to restrict the amount the player is able to move per turn. I need to make it so that the new velocity/position can only be a maximum of 20 px up/down and 20px left/right (20 px means pressing the arrow key twice).

Currently, the player moves according to the velocity set by the arrow key, but the velocity increases/decreases indefinitely along with the arrow keys. I need it to stop changing once the arrow keys have been pressed a maximum of 2 times in either direction (up/down, left/right).

Here's the code that controls the velocity:

```py
if event.type == pygame.KEYDOWN:
    if p1_turn:
        if event.key == pygame.K_RIGHT:
            p1_velocity_x += 10
        if event.key == pygame.K_LEFT:
                p1_velocity_x -= 10    

```

And here's the code that confirms the change (actually moves the player):

```py
if event.key == pygame.K_RETURN:
    if p1_turn:
        p1.y += p1_velocity_y
        p1.x += p1_velocity_x
        p1_turn = False
        p2_turn = True

```

As previously mentioned, there should be some mechanism to stop the velocity from going past 20px increase/decrease from the original x velocity and from the original y velocity.