You have another game under your belt, and I hope your brain is already starting to bubble up ideas for things you can do to improve it. Plus, you learned more skills, not least
-= operators, forcing method labels, plus lots of new
SKAction types, so it's all time well spent.
If you're looking to improve this project, you could start by adding a smoke-like particle effect to be used when the penguins are hit, and perhaps a separate mud-like effect when they go into or come out of a hole. You could also record your own voice saying "Game over!" and have it play when the game ends.
Try experimenting with the difficulty and see what you come up with – is it easier or harder if the penguin show/hide animation happens at random speeds?
One of the most effective motivators of success is sharing your progress with other people – when you tell folks what you're doing and what you've learned, it encourages you to come back for more, which in turn will help you reach your app development goals faster.
So, now that you've done all the hard work it's time to share your success: tell folks that you've completed this project, either by clicking the button below to start composing a tweet, or by writing your own message from scratch. This will definitely encourage you to keep learning, but it will also help other folks discover my work – thank you!
Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and Mario Kart world champion. OK, so that last part isn't true. If you're curious you can learn more here.