Wrap up

That's it! We just made a game in 20 minutes or so, which shows you just how fast SpriteKit is. I even showed you how per-pixel collision detection works (it's so easy!), how to advance particle systems so they start life with some history behind them, how to run code repeatedly using Timer, and how to adjust linear and angular damping so that objects don't slow down over time.

Review what you learned

Anyone can sit through a tutorial, but it takes actual work to remember what was taught. It’s my job to make sure you take as much from these tutorials as possible, so I’ve prepared a short review to help you check your learning.

Click here to review what you learned in project 17.

Challenge

One of the best ways to learn is to write your own code as often as possible, so here are three ways you should try your new knowledge to make sure you fully understand what’s going on:

1. Stop the player from cheating by lifting their finger and tapping elsewhere – try implementing touchesEnded() to make it work.
2. Make the timer start at one second, but then after 20 enemies have been made subtract 0.1 seconds from it so it’s triggered every 0.9 seconds. After making 20 more, subtract another 0.1, and so on. Note: you should call invalidate() on gameTimer before giving it a new value, otherwise you end up with multiple timers.
3. Stop creating space debris after the player has died.

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Share your success!

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!

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