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+# Advanced Features
+
+We've come a long way! By now, we've learned 99% of the things you'll need to
+know when writing Rust. Before we do one more project in Chapter 20, let's talk
+about a few things that you may run into that last 1% of the time. Feel free to
+skip this chapter and come back to it once you run into these things in the
+wild; the features we'll learn to use here are useful in very specific
+situations. We don't want to leave these features out, but you won't find
+yourself reaching for them often.
+
+In this chapter, we're going to cover:
+
+* Unsafe Rust: for when you need to opt out of some of Rust's guarantees and
+  tell the compiler that you will be responsible for upholding the guarantees
+  instead
+* Advanced Lifetimes: Additional lifetime syntax for complex situations
+* Advanced Traits: Associated Types, default type parameters, fully qualified
+  syntax, supertraits, and the newtype pattern in relation to traits
+* Advanced Types: some more about the newtype pattern, type aliases, the
+  "never" type, and dynamically sized types
+* Advanced Functions and Closures: function pointers and returning closures
+
+It's a panoply of Rust features with something for everyone! Let's dive in!