diff --git a/Brain/regex.md b/Brain/regex.md
index 5572d55..3704b9a 100644
--- a/Brain/regex.md
+++ b/Brain/regex.md
@@ -4,32 +4,53 @@ Read [Syntax](https://github.com/google/re2/wiki/Syntax).
 
 Read [Golang-Regex-Tutorial](https://github.com/StefanSchroeder/Golang-Regex-Tutorial).
 
-| regex    | meaning                                   |
-| -------- | ----------------------------------------- |
-| `.`      | any character, default not including `\n` |
-| `[xy]`   | `x` or `y` character                      |
-| `[^xy]`  | not `x` and `y` character                 |
-| `x`\|`y` | `x` or `y`                                |
-| `x*`     | 0 or more `x`, prefer **more**            |
-| `x+`     | 1 or more `x`, prefer **more**            |
-| `x?`     | 0 or 1 `x` , prefer 1                     |
-| `x*?`    | 0 or more `x`, prefer **fewer**           |
-| `x+?`    | 1 or more `x`, prefer **fewer**           |
-| `^`      | at beginning of text                      |
-| `$`      | at end of text                            |
-| `\d`     | digits                                    |
-| `\D`     | not digits                                |
-| `\s`     | whitespace                                |
-| `\S`     | not whitespace                            |
+Play with [Regex101](https://regex101.com/).
 
-| advanced regex | meaning                             |
-| -------------- | ----------------------------------- |
-| `(foo)`        | numbered capturing group (submatch) |
-| `(?:foo)`      | non capturing group                 |
-| `(?:x`\|`y)`   | `x` or `y` expression wrap in `()`  |
-| `(?flags)`     | set flags within current group      |
+## Basic
+
+| regex        | meaning                                   |
+| ------------ | ----------------------------------------- |
+| `.`          | any character, default not including `\n` |
+| `[xy]`       | `x` or `y` character                      |
+| `[^xy]`      | not `x` and `y` character                 |
+| `x`\|`y`     | `x` or `y`                                |
+| `x*`         | 0 or more `x`, prefer **more**            |
+| `x+`         | 1 or more `x`, prefer **more**            |
+| `x?`         | 0 or 1 `x` , prefer 1                     |
+| `x*?`        | 0 or more `x`, prefer **fewer**           |
+| `x+?`        | 1 or more `x`, prefer **fewer**           |
+| `^`          | at beginning of text                      |
+| `$`          | at end of text                            |
+| `\d`         | digits                                    |
+| `\D`         | not digits                                |
+| `\s`         | whitespace                                |
+| `\S`         | not whitespace                            |
+| `(foo)`      | numbered capturing group (submatch)       |
+| `(?:foo)`    | non capturing group                       |
+| `(?:x`\|`y)` | `x` or `y` expression wrap in `()`        |
+| `(?flags)`   | set flags within current group            |
 
 | flag | meaning          |
 | ---- | ---------------- |
 | `i`  | case-insensitive |
 | `s`  | `.` match `\n`   |
+
+## Example
+
+```regex
+(?i)hello\sfoo
+
+match: Hello Foo
+match: heLLo fOO
+```
+
+```regex
+hello\s(.+)
+
+match: hello foo
+group 1: foo
+
+
+match: hello bar
+group 1: bar
+```