# Help - Extension Building
**URL:** https://forum.makecode.com/t/help-extension-building/2106
**Category:** micro:bit
**Created:** [May 16, 2020, 3:38pm UTC](https://forum.makecode.com/t/help-extension-building/2106 "2020-05-16T15:38:41Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@DillonB07](https://forum.makecode.com/u/DillonB07)
#### Post date: [May 16, 2020, 3:38pm UTC](https://forum.makecode.com/t/help-extension-building/2106/1 "2020-05-16T15:38:41Z")
Hi
I’m developing an extension with GitHub and would like some help.
I am new to developing extensions and want to know how to add a block that turns on a certain amount of LEDs.
If you use the following link, you can see what I already have.
[https://github.com/dillonbarnes/microbit-screen-as-a-line](https://github.com/dillonbarnes/microbit-screen-as-a-line)
I’ve been using the BETA Deep Dive lessons on Mixer to help.
Please reply quickly.
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### Author:  [@peli](https://forum.makecode.com/u/peli)
#### Post date: [May 16, 2020, 3:52pm UTC](https://forum.makecode.com/t/help-extension-building/2106/2 "2020-05-16T15:52:42Z")
Here are the docs on custom blocks.
> **[Custom blocks](https://makecode.microbit.org/blocks/custom)**
>
> This page provides a short introduction to defining your own blocks in MakeCode.
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### Author:  [@peli](https://forum.makecode.com/u/peli)
#### Post date: [May 16, 2020, 3:54pm UTC](https://forum.makecode.com/t/help-extension-building/2106/3 "2020-05-16T15:54:12Z")
Looks like you got the gist of it. Do you already have a javascript function that turns on the led? Once you have it, you turn it into a block by adding the special comments.
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### Author:  [@DillonB07](https://forum.makecode.com/u/DillonB07)
#### Post date: [May 16, 2020, 4:05pm UTC](https://forum.makecode.com/t/help-extension-building/2106/4 "2020-05-16T16:05:12Z")
> Do not add block definitions directly into `main.ts` as they will show up as grey blocks. Instead, follow the steps below to add a new file, `custom.ts` , and add all your blocks in that file.
What does it mean by ‘grey blocks’?
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### Author:  [@DillonB07](https://forum.makecode.com/u/DillonB07)
#### Post date: [May 16, 2020, 4:07pm UTC](https://forum.makecode.com/t/help-extension-building/2106/7 "2020-05-16T16:07:17Z")
Are they just blocks that are visible, but won’t do anything?
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### Author:  [@DillonB07](https://forum.makecode.com/u/DillonB07)
#### Post date: [May 16, 2020, 4:10pm UTC](https://forum.makecode.com/t/help-extension-building/2106/8 "2020-05-16T16:10:37Z")
I’m building on your project that you made in Mixer and trying to create my own blocks using what you said on the stream.
I haven’t really done much.
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### Author:  [@peli](https://forum.makecode.com/u/peli)
#### Post date: [May 16, 2020, 5:23pm UTC](https://forum.makecode.com/t/help-extension-building/2106/9 "2020-05-16T17:23:05Z")
I will do a deep dive on custom blocks in the stream.
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### Author:  [@DillonB07](https://forum.makecode.com/u/DillonB07)
#### Post date: [May 16, 2020, 5:23pm UTC](https://forum.makecode.com/t/help-extension-building/2106/10 "2020-05-16T17:23:54Z")
Thanks!
I might not be able to watch live, but I’ll definitely watch it at some point in past streams.