Turn Around

Start the dot at column 35 so it reaches the wall quickly.

When it gets to the right-hand edge, flip dx to -1 so it heads back the other way. It only has to turn around once here — the left wall comes next.

Order matters: move first, then check whether you've arrived. Checking before you move tests where the dot used to be.

Expected output

36/1 37/1 38/1 39/-1 38/-1 37/-1 36/-1 35/-1

Need a hint?

3 available · costs 5 XP each

python

def new_game():

return {"x": 35, "dx": 1}

def update(state, keys):

state["x"] = state["x"] + state["dx"]

# If x has reached the right-hand wall, set dx to -1.

return state

def draw(state):

grid = blank_grid()

grid[6][state["x"]] = "red"

return grid