diff --git a/src/basic-types/char-bool-unit.md b/src/basic-types/char-bool-unit.md
index 98f104c..67462e8 100644
--- a/src/basic-types/char-bool-unit.md
+++ b/src/basic-types/char-bool-unit.md
@@ -12,6 +12,8 @@ fn main() {
 
     let c2 = '中';
     assert_eq!(size_of_val(&c2),3); 
+
+    println!("Success!")
 } 
 ```
 
@@ -33,13 +35,13 @@ fn print_char(c : char) {
 3. 🌟
 ```rust, editable
 
-// make the println! work
+// make println! work
 fn main() {
     let _f: bool = false;
 
     let t = true;
     if !t {
-        println!("hello, world");
+        println!("Success!")
     }
 } 
 ```
@@ -52,6 +54,8 @@ fn main() {
     let f = true;
     let t = true && false;
     assert_eq!(t, f);
+
+    println!("Success!")
 }
 ```
 
@@ -66,6 +70,8 @@ fn main() {
 
     let v = (2, 3);
     assert_eq!(v, implicitly_ret_unit())
+
+    println!("Success!")
 }
 
 fn implicitly_ret_unit() {
@@ -86,6 +92,8 @@ use std::mem::size_of_val;
 fn main() {
     let unit: () = ();
     assert!(size_of_val(&unit) == 4);
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/basic-types/functions.md b/src/basic-types/functions.md
index bab0197..e3cb022 100644
--- a/src/basic-types/functions.md
+++ b/src/basic-types/functions.md
@@ -8,6 +8,8 @@ fn main() {
     let s = sum(x, y);
 
     assert_eq!(s, 3);
+
+    println!("Success!")
 }
 
 fn sum(x, y: i32) {
@@ -24,7 +26,7 @@ fn main() {
 
 // replace i32 with another type
 fn print() -> i32 {
-   println!("hello,world");
+   println!("Success!")
 }
 ```
 
@@ -33,8 +35,11 @@ fn print() -> i32 {
 
 ```rust,editable
 // solve it in two ways
+// DON'T let `println!` works
 fn main() {
     never_return();
+
+    println!("Failed!")
 }
 
 fn never_return() -> ! {
diff --git a/src/basic-types/numbers.md b/src/basic-types/numbers.md
index 915a461..d0ccbbb 100644
--- a/src/basic-types/numbers.md
+++ b/src/basic-types/numbers.md
@@ -16,6 +16,8 @@ fn main() {
     y = x;
     
     let z = 10; // type of z ? 
+
+    println!("Success!")
 }
 ```
 
@@ -25,6 +27,8 @@ fn main() {
 //  fill the blank
 fn main() {
     let v: u16 = 38_u8 as __;
+
+    println!("Success!")
 }
 ```
 
@@ -38,6 +42,8 @@ fn main() {
 fn main() {
     let x = 5;
     assert_eq!("u32".to_string(), type_of(&x));
+
+    println!("Success!")
 }
 
 // get the type of given variable, return a string representation of the type  , e.g "i8", "u8", "i32", "u32"
@@ -53,6 +59,8 @@ fn type_of<T>(_: &T) -> String {
 fn main() {
     assert_eq!(i8::MAX, __); 
     assert_eq!(u8::MAX, __); 
+
+    println!("Success!")
 }
 ```
 
@@ -74,6 +82,8 @@ fn main() {
 fn main() {
     let v = 1_024 + 0xff + 0o77 + 0b1111_1111;
     assert!(v == 1579);
+
+    println!("Success!")
 }
 ```
 
@@ -88,6 +98,8 @@ fn main() {
     let x = 1_000.000_1; // ?
     let y: f32 = 0.12; // f32
     let z = 0.01_f64; // f64
+
+    println!("Success!")
 }
 ```
 
@@ -97,6 +109,8 @@ fn main() {
 
 fn main() {
     assert!(0.1+0.2==0.3);
+
+    println!("Success!")
 }
 ```
 
@@ -126,6 +140,8 @@ use std::ops::{Range, RangeInclusive};
 fn main() {
     assert_eq!((1..__), Range{ start: 1, end: 5 });
     assert_eq!((1..__), RangeInclusive::new(1, 5));
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/basic-types/statements-expressions.md b/src/basic-types/statements-expressions.md
index c144912..0d8f022 100644
--- a/src/basic-types/statements-expressions.md
+++ b/src/basic-types/statements-expressions.md
@@ -35,6 +35,8 @@ fn main() {
    };
 
    assert_eq!(v, 3);
+
+   println!("Success!")
 }
 ```
 
@@ -45,6 +47,8 @@ fn main() {
    let v = (let x = 3);
 
    assert!(v == 3);
+
+   println!("Success!")
 }
 ```
 
@@ -54,6 +58,8 @@ fn main() {
 fn main() {
     let s = sum(1 , 2);
     assert_eq!(s, 3);
+
+    println!("Success!")
 }
 
 fn sum(x: i32, y: i32) -> i32 {
diff --git a/src/compound-types/array.md b/src/compound-types/array.md
index 321fe6c..92104e1 100644
--- a/src/compound-types/array.md
+++ b/src/compound-types/array.md
@@ -19,6 +19,8 @@ fn main() {
 
     // modify below to make it work
     assert!(arr.len() == 4);
+
+    println!("Success!")
 }
 ```
 
@@ -34,6 +36,8 @@ fn main() {
     // Arrays are stack allocated, `std::mem::size_of_val` return the bytes which array occupies
     // A char takes 4 byte in Rust: Unicode char
     assert!(std::mem::size_of_val(&arr) == __);
+
+    println!("Success!")
 }
 ```
 
@@ -47,6 +51,8 @@ fn main() {
 
     assert!(list[0] == 1);
     assert!(list.len() == 100);
+
+    println!("Success!")
 }
 ```
 
@@ -56,6 +62,8 @@ fn main() {
 fn main() {
     // fix the error
     let _arr = [1, 2, '3'];
+
+    println!("Success!")
 }
 ```
 
@@ -68,6 +76,8 @@ fn main() {
     let ele = arr[1]; // only modify this line to make the code work!
 
     assert!(ele == 'a');
+
+    println!("Success!")
 }
 ```
 
@@ -83,6 +93,8 @@ fn main() {
 
     // but indexing is not safe
     let _name1 = &names[2];
+
+    println!("Success!")
 }
 
 ```
diff --git a/src/compound-types/enum.md b/src/compound-types/enum.md
index 092492f..2fba9cf 100644
--- a/src/compound-types/enum.md
+++ b/src/compound-types/enum.md
@@ -28,6 +28,8 @@ fn main() {
     // a enum variant can be converted to a integer by `as`
     assert_eq!(Number::One, Number1::One);
     assert_eq!(Number1::One, Number2::One);
+
+    println!("Success!")
 } 
 ```
 
@@ -45,6 +47,8 @@ enum Message {
 fn main() {
     let msg1 = Message::Move{__}; // instantiating with x = 1, y = 2 
     let msg2 = Message::Write(__); // instantiating with "hello, world!"
+
+    println!("Success!")
 } 
 ```
 
@@ -67,6 +71,8 @@ fn main() {
     } else {
         panic!("NEVER LET THIS RUN！");
     }
+
+    println!("Success!")
 } 
 ```
 
diff --git a/src/compound-types/slice.md b/src/compound-types/slice.md
index 85ad192..2c4c0ec 100644
--- a/src/compound-types/slice.md
+++ b/src/compound-types/slice.md
@@ -10,6 +10,8 @@ fn main() {
     let s1: [i32] = arr[0..2];
 
     let s2: str = "hello, world" as str;
+
+    println!("Success!")
 }
 ```
 
@@ -26,6 +28,8 @@ fn main() {
     // modify '6' to make it work
     // TIPS: slice( reference ) IS NOT an array, if it is an array, then `assert!` will passed: each of the two UTF-8 chars '中' and '国'  occupies 3 bytes, 2 * 3 = 6
     assert!(std::mem::size_of_val(&slice) == 6);
+
+    println!("Success!")
 }
 ```
 
@@ -37,6 +41,8 @@ fn main() {
   // fill the blanks to make the code work
   let slice: __ = __;
   assert_eq!(slice, &[2, 3, 4]);
+
+  println!("Success!")
 }
 ```
 
@@ -52,6 +58,8 @@ fn main() {
     let slice2 = &s[__];
 
     assert_eq!(slice1, slice2);
+
+    println!("Success!")
 }
 ```
 
@@ -64,6 +72,8 @@ fn main() {
     let slice = &s[0..2];
 
     assert!(slice == "你");
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/compound-types/string.md b/src/compound-types/string.md
index fdb29bb..76bfc1f 100644
--- a/src/compound-types/string.md
+++ b/src/compound-types/string.md
@@ -10,6 +10,8 @@ The type of string literal `"hello, world"` is `&str`, e.g `let s: &str = "hello
 // fix error without adding new line
 fn main() {
    let s: str = "hello, world";
+
+   println!("Success!")
 }
 ```
 
@@ -42,6 +44,8 @@ fn main() {
    s.push('!');
 
    assert_eq!(s, "hello, world!");
+
+   println!("Success!")
 }
 ```
 
@@ -68,7 +72,9 @@ fn main() {
    // Allocate new memory and store the modified string there
    let s1 = s.__("dogs", "cats");
 
-   assert_eq!(s1, "I like cats")
+   assert_eq!(s1, "I like cats");
+
+   println!("Success!")
 }
 ```
 
@@ -113,6 +119,8 @@ fn greetings(s: String) {
 fn main() {
    let s =  "hello, world".to_string();
    let s1: &str = s;
+
+   println!("Success!")
 }
 ```
 
@@ -222,6 +230,8 @@ fn main() {
 
     let h1 = &s1[3..5];//modify this line to fix the error, tips: `中`  takes 3 bytes in UTF8 format
     assert_eq!(h1, "中");
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/compound-types/struct.md b/src/compound-types/struct.md
index 7061f44..00dece8 100644
--- a/src/compound-types/struct.md
+++ b/src/compound-types/struct.md
@@ -16,6 +16,8 @@ fn main() {
         name: String::from("sunface"),
         age,
     };
+
+    println!("Success!")
 } 
 ```
 
@@ -34,6 +36,8 @@ impl SomeTrait for Unit {  }
 fn main() {
     let u = Unit;
     do_something_with_unit(u);
+
+    println!("Success!")
 } 
 
 // fill the blank to make the code work
@@ -50,6 +54,8 @@ struct Point(i32, i32, i32);
 fn main() {
     let v = Point(__, __, __);
     check_color(v);
+
+    println!("Success!")
 }   
 
 fn check_color(p: Color) {
@@ -83,6 +89,8 @@ fn main() {
 
     // fill the lank
     __ = String::from("sunfei");
+
+    println!("Success!")
 }
 ```
 
@@ -94,7 +102,9 @@ struct Person {
     name: String,
     age: u8,
 }
-fn main() {} 
+fn main() {
+    println!("Success!")
+} 
 
 fn build_person(name: String, age: u8) -> Person {
     Person {
@@ -123,6 +133,8 @@ fn main() {
     };
 
     let u2 = set_email(u1);
+
+    println!("Success!")
 } 
 
 fn set_email(u: User) -> User {
diff --git a/src/compound-types/tuple.md b/src/compound-types/tuple.md
index df793a5..3912eb6 100644
--- a/src/compound-types/tuple.md
+++ b/src/compound-types/tuple.md
@@ -8,6 +8,8 @@ fn main() {
     let _t1: (u8, (i16, u32)) = (0, (-1, 1));
     // fill the blanks to make the code work
     let t: (u8, __, i64, __, __) = (1u8, 2u16, 3i64, "hello", String::from(", world"));
+
+    println!("Success!")
 }
 ```
 
@@ -18,6 +20,8 @@ fn main() {
 fn main() {
    let t = ("i", "am", "sunface");
    assert_eq!(t.1, "sunface");
+
+   println!("Success!")
 }
 ```
 
@@ -43,6 +47,8 @@ fn main() {
     assert_eq!(x, 1);
     assert_eq!(y, "hello");
     assert_eq!(z, 6.4);
+
+    println!("Success!")
 }
 ```
 
@@ -57,6 +63,8 @@ fn main() {
     assert_eq!(x, 3);
     assert_eq!(y, 1);
     assert_eq!(z, 2);
+
+    println!("Success!")
 }
 ```
 
@@ -69,6 +77,8 @@ fn main() {
 
    assert_eq!(x, 5);
    assert_eq!(y, 6);
+
+   println!("Success!")
 }
 
 fn sum_multiply(nums: (i32, i32)) -> (i32, i32) {
diff --git a/src/flow-control.md b/src/flow-control.md
index 33b2bfb..ac19d87 100644
--- a/src/flow-control.md
+++ b/src/flow-control.md
@@ -51,6 +51,8 @@ fn main() {
             panic!("NEVER LET THIS RUN")
         }
     }
+
+    println!("Success!")
 } 
 ```
 
@@ -134,6 +136,8 @@ fn main() {
     }
 
     assert_eq!(n, 66);
+
+    println!("Success!")
 }
 ```
 
@@ -153,6 +157,8 @@ fn main() {
     }
 
     assert_eq!(n, 66);
+
+    println!("Success!")
 }
 ```
 
@@ -189,6 +195,8 @@ fn main() {
     }
 
     assert_eq!(count, 5);
+
+    println!("Success!")
 }
 ```
 
@@ -208,6 +216,8 @@ fn main() {
     };
 
     assert_eq!(result, 20);
+
+    println!("Success!")
 }
 ```
 
@@ -240,7 +250,9 @@ fn main() {
         }
     }
 
-    assert!(count == __)
+    assert!(count == __);
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/generics-traits/const-generics.md b/src/generics-traits/const-generics.md
index 45b8a95..90605ee 100644
--- a/src/generics-traits/const-generics.md
+++ b/src/generics-traits/const-generics.md
@@ -88,6 +88,8 @@ fn main() {
             data: [1, 2]
         }
     ];
+
+    println!("Success!")
 }
 ```
 
@@ -127,6 +129,8 @@ fn main() {
     check_size(["hello你好"; __]); // size of &str ?
     check_size(["hello你好".to_string(); __]);  // size of String?
     check_size(['中'; __]); // size of char ?
+
+    println!("Success!")
 }
 
 
diff --git a/src/generics-traits/generics.md b/src/generics-traits/generics.md
index 1896f48..dce2a14 100644
--- a/src/generics-traits/generics.md
+++ b/src/generics-traits/generics.md
@@ -28,6 +28,8 @@ fn main() {
 
     // Implicitly specified type parameter `char` to `generic()`.
     generic(__);
+
+    println!("Success!")
 }
 ```
 
@@ -41,6 +43,8 @@ fn main() {
     assert_eq!(5, sum(2i8, 3i8));
     assert_eq!(50, sum(20, 30));
     assert_eq!(2.46, sum(1.23, 1.23));
+
+    println!("Success!")
 }
 ```
 
@@ -56,6 +60,8 @@ fn main() {
 fn main() {
     let integer = Point { x: 5, y: 10 };
     let float = Point { x: 1.0, y: 4.0 };
+
+    println!("Success!")
 }
 ```
 
@@ -71,6 +77,8 @@ struct Point<T> {
 fn main() {
     // DON'T modify here
     let p = Point{x: 5, y : "hello".to_string()};
+
+    println!("Success!")
 }
 ```
 
@@ -118,6 +126,8 @@ fn main() {
 
     assert_eq!(p3.x, 5);
     assert_eq!(p3.y, '中');
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/generics-traits/traits.md b/src/generics-traits/traits.md
index b074453..c0b1e9c 100644
--- a/src/generics-traits/traits.md
+++ b/src/generics-traits/traits.md
@@ -106,6 +106,8 @@ fn main() {
     let t = Teacher {};
     assert_eq!(t.say_hi(), "Hi, I'm your new teacher");
     assert_eq!(t.say_something(), "I'm not a bad teacher");
+
+    println!("Success!")
 }
 ```
 
@@ -177,6 +179,8 @@ fn multipl
 fn main() {
     assert_eq!(6, multiply(2u8, 3u8));
     assert_eq!(5.0, multiply(1.0, 5.0));
+
+    println!("Success!")
 }
 ```
 
@@ -217,6 +221,8 @@ fn main() {
     // you need to derive some trait for FooBar to make it comparable
     assert_eq!(Foo + Bar, FooBar);
     assert_eq!(Foo - Bar, BarFoo);
+
+    println!("Success!")
 }
 ```
 
@@ -456,5 +462,7 @@ fn example2() {
 fn main() {
     example1();
     example2();
+
+    println!("Success!")
 }
 ```
\ No newline at end of file
diff --git a/src/method.md b/src/method.md
index 6f7d977..477ddcc 100644
--- a/src/method.md
+++ b/src/method.md
@@ -132,6 +132,8 @@ fn main() {
     let rect1 = Rectangle { width: 30, height: 50 };
 
     assert_eq!(rect1.area(), 1500);
+
+    println!("Success!")
 }
 ```
 
@@ -176,7 +178,9 @@ impl TrafficLight {
         self.color = "green".to_string()
     }
 }
-fn main() {}
+fn main() {
+    println!("Success!")
+}
 ```
 
 
@@ -204,6 +208,8 @@ impl TrafficLight {
 fn main() {
     let light = TrafficLight::new();
     assert_eq!(light.get_state(), "red");
+
+    println!("Success!")
 }
 ```
 
@@ -228,7 +234,9 @@ impl Rectangle {
 }
 
 
-fn main() {}
+fn main() {
+    println!("Success!")
+}
 ```
 
 ### Enums
diff --git a/src/ownership/borrowing.md b/src/ownership/borrowing.md
index 1d5b87c..e5a2903 100644
--- a/src/ownership/borrowing.md
+++ b/src/ownership/borrowing.md
@@ -22,6 +22,8 @@ fn main() {
 
     // modify this line only
     assert_eq!(5, y);
+
+    println!("Success!")
 }
 ```
 
@@ -45,7 +47,9 @@ fn borrow_object(s: &String) {}
 fn main() {
     let mut s = String::from("hello, ");
 
-    push_str(s)
+    push_str(s);
+
+    println!("Success!")
 }
 
 fn push_str(s: &mut String) {
@@ -63,6 +67,8 @@ fn main() {
     let p = __;
     
     p.push_str("world");
+
+    println!("Success!")
 }
 ```
 
@@ -83,6 +89,8 @@ fn main() {
     
     // check the equality of the two address strings
     assert_eq!(get_addr(r1),get_addr(r2));
+
+    println!("Success!")
 }
 
 // get memory address string
@@ -104,6 +112,8 @@ fn main() {
     let r2 = &mut s;
 
     println!("{}, {}", r1, r2);
+
+    println!("Success!")
 }
 ```
 
@@ -116,6 +126,8 @@ fn main() {
     let  s = String::from("hello, ");
 
     borrow_object(&mut s)
+
+    println!("Success!")
 }
 
 fn borrow_object(s: &mut String) {}
@@ -131,6 +143,8 @@ fn main() {
     borrow_object(&s);
     
     s.push_str("world");
+
+    println!("Success!")
 }
 
 fn borrow_object(s: &String) {}
diff --git a/src/ownership/ownership.md b/src/ownership/ownership.md
index af3d881..7bfac60 100644
--- a/src/ownership/ownership.md
+++ b/src/ownership/ownership.md
@@ -84,6 +84,8 @@ fn main() {
     let s1 = s;
 
     s1.push_str("world")
+
+    println!("Success!")
 }
 ```
 
@@ -98,6 +100,8 @@ fn main() {
     *y = 4;
     
     assert_eq!(*x, 5);
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/pattern-match/match-iflet.md b/src/pattern-match/match-iflet.md
index 2ed54eb..e4c3c3f 100644
--- a/src/pattern-match/match-iflet.md
+++ b/src/pattern-match/match-iflet.md
@@ -37,6 +37,8 @@ fn main() {
     let binary = __;
 
     assert_eq!(binary, 1);
+
+    println!("Success!")
 }
 ```
 
@@ -61,6 +63,8 @@ fn main() {
     for msg in msgs {
         show_message(msg)
     }
+
+    println!("Success!")
 } 
 
 fn show_message(msg: Message) {
@@ -91,6 +95,8 @@ fn main() {
     for ab in alphabets {
         assert!(__)
     }
+
+    println!("Success!")
 } 
 ```
 
@@ -113,6 +119,8 @@ fn main() {
     }
 
     assert_eq!(count, 2);
+
+    println!("Success!")
 }
 ```
 
@@ -129,6 +137,8 @@ fn main() {
     match o {
         Some(i) => {
             println!("This is a really long string and `{:?}`", i);
+
+            println!("Success!")
         }
         _ => {}
     };
@@ -148,6 +158,8 @@ fn main() {
 
     __ {
         println!("foobar holds the value: {}", i);
+
+        println!("Success!")
     }
 }
 ```
diff --git a/src/pattern-match/patterns.md b/src/pattern-match/patterns.md
index bf65bd8..d438705 100644
--- a/src/pattern-match/patterns.md
+++ b/src/pattern-match/patterns.md
@@ -78,6 +78,8 @@ fn main() {
         Some(x) => assert!(x >= split),
         None => (),
     }
+
+    println!("Success!")
 }
 ```
 
@@ -94,6 +96,8 @@ fn main() {
            assert_eq!(last, 2048);
         }
     }
+
+    println!("Success!")
 }
 ```
 
diff --git a/src/variables.md b/src/variables.md
index c977e43..43ad6c5 100644
--- a/src/variables.md
+++ b/src/variables.md
@@ -8,7 +8,9 @@
 fn main() {
     let x: i32; // uninitialized but using, ERROR !
     let y: i32; // uninitialized but also unusing, only warning
-    println!("{} is equal to 5", x); 
+
+    assert_eq!(x, 5);
+    println!("Success!")
 }
 ```
 
@@ -20,7 +22,8 @@ fn main() {
     let __ =  1;
     __ += 2; 
     
-    println!("{} is equal to 3", x); 
+    assert_eq!(x, 3);
+    println!("Success!")
 }
 ```
 
@@ -90,6 +93,8 @@ fn main() {
     let y = 4;
     // shadowing
     let y = "I can also be bound to text!"; 
+
+    println!("Success!")
 }
 ```
 
@@ -124,6 +129,8 @@ fn main() {
 
     assert_eq!(x, 3);
     assert_eq!(y, 2);
+
+    println!("Success!")
 }
 ```
 
@@ -142,6 +149,8 @@ fn main() {
     [.., y] = [1, 2];
     // fill the blank to make the code work
     assert_eq!([x,y], __);
+
+    println!("Success!")
 } 
 ```
 
diff --git a/zh-CN/src/basic-types/char-bool-unit.md b/zh-CN/src/basic-types/char-bool-unit.md
index 9437bda..8b90ff9 100644
--- a/zh-CN/src/basic-types/char-bool-unit.md
+++ b/zh-CN/src/basic-types/char-bool-unit.md
@@ -11,6 +11,8 @@ fn main() {
 
     let c2 = '中';
     assert_eq!(size_of_val(&c2),3); 
+
+    println!("Success!")
 } 
 ```
 
@@ -31,13 +33,13 @@ fn print_char(c : char) {
 3. 🌟
 ```rust, editable
 
-// 让  println! 工作
+// make  println! work
 fn main() {
     let _f: bool = false;
 
     let t = true;
     if !t {
-        println!("hello, world");
+        println!("Success!")
     }
 } 
 ```
@@ -49,6 +51,8 @@ fn main() {
     let f = true;
     let t = true && false;
     assert_eq!(t, f);
+
+    println!("Success!")
 }
 ```
 
@@ -63,6 +67,8 @@ fn main() {
 
     let v = (2, 3);
     assert_eq!(v, implicitly_ret_unit())
+
+    println!("Success!")
 }
 
 fn implicitly_ret_unit() {
@@ -83,6 +89,8 @@ use std::mem::size_of_val;
 fn main() {
     let unit: () = ();
     assert!(size_of_val(&unit) == 4);
+
+    println!("Success!")
 }
 ```