6.3.5 Cmu Cs Academy -

This is where the actual movement happens.

def onStep(app):
    # If the flag is true, move the shape by a small amount
    if app.movingRight == True:
        app.player.centerX += 5
if app.movingLeft == True:
    app.player.centerX -= 5

A common prompt (reconstructed from typical CMU CS Academy content):

"Write a program where a blue circle moves right across the screen. It should stop when its center reaches x = 300. Use a while loop inside onStep or a custom function. Ensure the loop doesn't freeze the program." 6.3.5 Cmu Cs Academy

Constraints:

If you only use onKeyPress, your shape will move once, pause, and then move again (because of the computer's key-repeat delay). This feels "jerky." The Solution: You need a helper variable (Boolean) to track if the key is held down. This is where the actual movement happens

Error: Using range(rows-1) or range(1, rows).
Result: Missing the first or last row/column.
Fix: Always use range(rows) and range(cols) for full coverage.

In the real world, the pattern you learn in 6.3.5 is everywhere: A common prompt (reconstructed from typical CMU CS

Understanding onKeyPress and global state is your first step toward building a playable game in CMU CS Academy—like a simple maze or a "catch the falling objects" game.