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Exercise 2 · Chapter: Press to FlapRequired+50 XP

It Falls Down

Same falling you wrote in Chapter 4, now upside down.

The hero starts at height 6. Each frame:

  1. move: add vy to y
  2. gravity: take 1 off vy
  3. floor: if y dropped below 0, put it back to 0 and zero vy

Because y is a height, gravity subtracts from vy instead of adding. The hero drops faster and faster until it lands, and then stays put.

The trace prints y/vy. Watch the height drop 6, 5, 3, 0 — bigger gaps each frame, because vy keeps growing more negative — and then stay on the ground.

You may notice vy twitching between 0 and -1 once it has landed. That's gravity still pulling on something that is already resting: the floor check only fires when y would go below zero. It never moves the hero, so it does no harm. Real games are full of small idling details like this.

Expected output
6/-1 5/-2 3/-3 0/-4 0/0 0/-1
Need a hint?
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python
def new_game():
return {"y": 6, "vy": 0}


def update(state, keys):
# Move by vy, then subtract 1 from vy, then stop at the ground.
return state


def draw(state):
grid = blank_grid()
grid[GROUND - state["y"]][6] = "gold"
return grid