To run the site with Twoslash enabled you need to use yarn start-twoslash.
Code samples on the TypeScript Website should run through Twoslash which lets the compiler do more of the work.
Without twoslash a code sample looks like:
```ts
// Declare a tuple type
let x: [string, number];
// Initialize it
x = ["hello", 10]; // OK
// Initialize it incorrectly
x = [10, "hello"]; // Error
```
With twoslash:
```ts twoslash
// Declare a tuple type
let x: [string, number];
// Initialize it
x = ["hello", 10]; // OK
// Initialize it incorrectly
x = [10, "hello"]; // Error
```
This would now break the TypeScript website build because the code sample has a compiler error, this is great. Let's fix that by telling TypeScript this error is on purpose:
```ts twoslash
// @errors: 2322
// Declare a tuple type
let x: [string, number];
// Initialize it
x = ["hello", 10]; // OK
// Initialize it incorrectly
x = [10, "hello"]; // Error
```
Now it will pass. The thing from here is that the comments are kind redundant because the compiler will tell you that info, so let's trim those:
```ts twoslash
// @errors: 2322
// Declare a tuple type
let x: [string, number];
// Initialize it
x = ["hello", 10];
// Initialize it incorrectly
x = [10, "hello"];
```
A twoslash code sample can do a lot - the best documentation for twoslash lives inside the bug workbench where you can test your code sample live and read how it all works.