I believe the concept was well applied and it gets really challenging immediately in the beginning with so many rockets. Think you could scale it depending on the score the player currently has, getting harder every time.
Another thing I noticed is that, after collecting all the bottles, the player would only be left dodging the rockets without being able to score more points and increase my high score. Not sure if it was a bug or if a bottle spawner was never implemented.
Would recommend using a spawn mechanic similar to Snake, that when a bottle is collected, another would spawn, and you could even make it look like someone threw the bottles from the buildings above, so they don't just magically appear.
Fun concept and a challenging game either way. Congrats!