update why-exercise.md

src/why-exercise.md

@@ -1,25 +1,35 @@
 # Rust By Practice
-This book was designed for easily diving into Rust，and it's very easy to use: All you need to do is to make each exercise compile without ERRORS and Panics !
+
-  
+This book was designed for easily diving into Rust, and it's very easy to use: All you need to do is to make each exercise compile without ERRORS and Panics !
+
+## Read online
+
+- [English](https://practice.rs)
+- [简体中文](https://zh.practice.rs)
+
 ## Features
 
-- There are three parts in each chapter: examples, exercises and practices
+Part of our examples and exercises are borrowed from [Rust By Example](https://github.com/rust-lang/rust-by-example), thanks for your great works!
-  
-- Covering nearly all aspects of Rust, such as **async/await, threads, sync primitives, optimizing and stand libraries** etc
-  
-- Solution for each exercise
-  
-- Difficulty from easy to super hard: easy 🌟  medium 🌟🌟 hard 🌟🌟🌟  super hard 🌟🌟🌟🌟
-  
-- Both [English](https://practice.rs) and [Chinsese](https://zh.practice.rs) are supported
 
-> Part of our examples and exercises are borrowed from [Rust By Example](https://github.com/rust-lang/rust-by-example), thanks for the great works you have been doing!
+Although they are so awesome, we have our own secret weapons :)
+
+- There are three parts in each chapter: examples, exercises and practices
+
+- Besides examples, we have `a lot of exercises`, you can Read, Edit and Run them ONLINE
+
+- Covering nearly all aspects of Rust, such as async/await, threads, sync primitives, optimizing and standard libraries** etc.
+
+- Every exercise has its own solutions
+
+- The overall difficulties are a bit higher and from easy to super hard: easy 🌟 medium 🌟🌟 hard 🌟🌟🌟 super hard 🌟🌟🌟🌟
+
+**What we want to do is fill in the gap between learning and getting started with real projects.**
 
 ## Some of our exercises
 
 🌟🌟🌟 Tuple struct looks similar to tuples, it has added meaning the struct name provides but has no named fields. It's useful when you want give the whole tuple a name, but don't care the fields's names.
 
-```rust,editable
+```rust
 
 // fix the error and fill the blanks
 struct Color(i32, i32, i32);
@@ -27,7 +37,7 @@ struct Point(i32, i32, i32);
 fn main() {
     let v = Point(___, ___, ___);
     check_color(v);
-}   
+}
 
 fn check_color(p: Color) {
     let (x, _, _) = p;
@@ -38,7 +48,7 @@ fn check_color(p: Color) {
 ```
 
 🌟🌟 Within the destructuring of a single variable, both by-move and by-reference pattern bindings can be used at the same time. Doing this will result in a partial move of the variable, which means that parts of the variable will be moved while other parts stay. In such a case, the parent variable cannot be used afterwards as a whole, however the parts that are only referenced (and not moved) can still be used.
-```rust,editable
+```rust
 
 // fix errors to make it work
 #[derive(Debug)]
@@ -56,7 +66,7 @@ fn main() {
 
     // ONLY modify this line
     println!("{}, {}, {:?}",f.name, f.data, f);
-} 
+}
 ```
 
 🌟🌟 A match guard is an additional if condition specified after the pattern in a match arm that must also match, along with the pattern matching, for that arm to be chosen.