* [**C++**: *Introduction to Ray Tracing: a Simple Method for Creating 3D Images*](https://www.scratchapixel.com/lessons/3d-basic-rendering/introduction-to-ray-tracing/how-does-it-work)
* [**C++**: *How OpenGL works: software rendering in 500 lines of code*](https://github.com/ssloy/tinyrenderer/wiki)
* [**Java + JavaScript**: *Build your own 3D renderer*](https://avik-das.github.io/build-your-own-raytracer/)
* [**Java**: *How to create your own simple 3D render engine in pure Java*](http://blog.rogach.org/2015/08/how-to-create-your-own-simple-3d-render.html)
* [**Ethereum**: *From “What is Blockchain?” to building a blockchain in less than an hour*](https://medium.freecodecamp.org/from-what-is-blockchain-to-building-a-blockchain-within-an-hour-4e738efc819d)
* [**Haskell**: *A simple cryptocurrency implementation, written to illustrate the basic components of a Proof-of-Work based public distributed ledger*](https://github.com/adjoint-io/nanocoin)
* [**Java**: *Creating Your First Blockchain with Java*](https://medium.com/programmers-blockchain/create-simple-blockchain-java-tutorial-from-scratch-6eeed3cb03fa)
* [**JavaScript**: *A cryptocurrency implementation in less than 1500 lines of code*](https://github.com/conradoqg/naivecoin)
* [**JavaScript**: *Build your own Blockchain in Javascript*](https://github.com/nambrot/blockchain-in-js)
* [**JavaScript**: *Learn & Build a Javascript Blockchain*](https://medium.com/digital-alchemy-holdings/learn-build-a-javascript-blockchain-part-1-ca61c285821e)
* [**Python**: *Learn Blockchains by Building One*](https://hackernoon.com/learn-blockchains-by-building-one-117428612f46)
* [**Python**: *Build your own blockchain: a Python tutorial*](http://ecomunsing.com/build-your-own-blockchain)
* [**TypeScript**: *Naivecoin: a tutorial for building a cryptocurrency*](https://lhartikk.github.io/)
#### Build your own `Bot`
* [**Haskell**: *Roll your own IRC bot*](https://wiki.haskell.org/Roll_your_own_IRC_bot)
* [**Java**: *How To Make a Scary Russian Twitter Bot With Java*](https://medium.com/@SeloSlav/how-to-make-a-scary-russian-twitter-bot-with-java-b7b62768a3ac)
* [**Node.js**: *Creating a Simple Facebook Messenger AI Bot with API.ai in Node.js*](https://tutorials.botsfloor.com/creating-a-simple-facebook-messenger-ai-bot-with-api-ai-in-node-js-50ae2fa5c80d)
* [**Node.js**: *Why you should have your own Twitter bot, and how to build one in less than 30 minutes*](https://medium.freecodecamp.org/easily-set-up-your-own-twitter-bot-4aeed5e61f7f)
* [**Node.js**: *How to make a responsive telegram bot*](https://www.sohamkamani.com/blog/2016/09/21/making-a-telegram-bot/)
* [**Node.js**: *Create a Discord bot*](https://discordjs.guide/)
* [**PHP**: *Let’s write a cryptocurrency bot*](https://medium.com/@joeldg/an-advanced-tutorial-a-new-crypto-currency-trading-bot-boilerplate-framework-e777733607ae)
* [**Python**: *Step-by-Step Instructions for Building a Basic Facebook Chat Bot*](https://blog.hartleybrody.com/fb-messenger-bot/)
* [**Python**: *Build a Reddit Bot*](http://pythonforengineers.com/build-a-reddit-bot-part-1/)
* [**Python**: *How To Make A reddit Bot*](https://www.youtube.com/watch?v=krTUf7BpTc0) [video]
* [**Python**: *How To Create a Telegram Bot Using Python*](https://khashtamov.com/en/how-to-create-a-telegram-bot-using-python/)
* [**Python**: *Create a Twitter Bot in Python Using Tweepy*](https://medium.freecodecamp.org/creating-a-twitter-bot-in-python-with-tweepy-ac524157a607)
* [**R**: *Build A Cryptocurrency Trading Bot with R*](https://towardsdatascience.com/build-a-cryptocurrency-trading-bot-with-r-1445c429e1b1)
* [**JavaScript**: *Building React From Scratch*](https://www.youtube.com/watch?v=_MAD4Oly9yg) [video]
* [**JavaScript**: *Building Your Own React Clone in Five Easy Steps*](https://blog.javascripting.com/2016/10/05/building-your-own-react-clone-in-five-easy-steps/)
* [**JavaScript**: *Build your own Vuejs*](https://github.com/jsrebuild/build-your-own-vuejs)
* [**JavaScript**: *Build Yourself a Redux*](https://zapier.com/engineering/how-to-build-redux/)
* [**JavaScript**: *Redux: Implementing Store from Scratch*](https://egghead.io/lessons/react-redux-implementing-store-from-scratch)
* [**JavaScript**: *Build Your own Simplified AngularJS in 200 Lines of JavaScript*](https://blog.mgechev.com/2015/03/09/build-learn-your-own-light-lightweight-angularjs/)
* [**JavaScript**: *How to write your own Virtual DOM*](https://medium.com/@deathmood/how-to-write-your-own-virtual-dom-ee74acc13060)
#### Build your own `Docker`
* [**C**: *Linux containers in 500 lines of code*](https://blog.lizzie.io/linux-containers-in-500-loc.html)
* [**Go**: *Building a container from scratch in Go*](https://www.youtube.com/watch?v=Utf-A4rODH8) [video]
* [**Python**: *A workshop on Linux containers: Rebuild Docker from Scratch*](https://github.com/Fewbytes/rubber-docker)
* [**Python**: *A proof-of-concept imitation of Docker, written in 100% Python*](https://github.com/tonybaloney/mocker)
* [**Shell**: *Docker implemented in around 100 lines of bash*](https://github.com/p8952/bocker)
* [**Go**: *Build a multilayer perceptron with Golang*](https://made2591.github.io/posts/neuralnetwork)
* [**Go**: *How to build a simple artificial neural network with Go*](https://sausheong.github.io/posts/how-to-build-a-simple-artificial-neural-network-with-go/)
* [**Go**: *Building a Neural Net from Scratch in Go*](https://www.datadan.io/building-a-neural-net-from-scratch-in-go/)
* [**JavaScript**: *Neural Network implementation in Javascript, by an example*](https://franpapers.com/en/machine-learning-ai-en/2017-neural-network-implementation-in-javascript-by-an-example/)
* [**JavaScript**: *Neural networks from scratch for Javascript linguists (Part1—The Perceptron)*](https://hackernoon.com/neural-networks-from-scratch-for-javascript-linguists-part1-the-perceptron-632a4d1fbad2)
* [**JavaScript**: *You can build a neural network in JavaScript even if you don’t really understand neural networks*](https://itnext.io/you-can-build-a-neural-network-in-javascript-even-if-you-dont-really-understand-neural-networks-e63e12713a3)
* [**JavaScript**: *How to create a Neural Network in JavaScript in only 30 lines of code*](https://medium.freecodecamp.org/how-to-create-a-neural-network-in-javascript-in-only-30-lines-of-code-343dafc50d49)
* [**Python**: *Optical Character Recognition (OCR)*](http://aosabook.org/en/500L/optical-character-recognition-ocr.html)
#### Build your own `Network Stack`
* [**C**: *Beej's Guide to Network Programming*](http://beej.us/guide/bgnet/html/multi/index.html)
* [**C**: *Let's code a TCP/IP stack*](http://www.saminiir.com/lets-code-tcp-ip-stack-1-ethernet-arp/)
* [**Ruby**: *How to build a network stack in Ruby*](https://medium.com/geckoboard-under-the-hood/how-to-build-a-network-stack-in-ruby-f73aeb1b661b)
#### Build your own `Operating System`
* [**Assembly**: *Writing a Tiny x86 Bootloader*](http://joebergeron.io/posts/post_two.html)
* [**C**: *Operating Systems: From 0 to 1*](https://tuhdo.github.io/os01/)
* [**C**: *The little book about OS development*](https://littleosbook.github.io/)
* [**C**: *Kernel 101 –Let’s write a Kernel*](https://arjunsreedharan.org/post/82710718100/kernel-101-lets-write-a-kernel)
* [**C**: *Build a minimal multi-tasking kernel for ARM from scratch*](https://github.com/jserv/mini-arm-os)
* [**C**: *How to create an OS from scratch*](https://github.com/cfenollosa/os-tutorial)
* [**Ruby**: *How to write a template engine in less than 30 lines of code*](http://bits.citrusbyte.com/how-to-write-a-template-library/)
#### Build your own `Web Server`
* [**C#**: *Writing a Web Server from Scratch*](https://www.codeproject.com/Articles/859108/Writing-a-Web-Server-from-Scratch)
* [**Node.js**: *Let's code a web server from scratch with NodeJS Streams*](https://www.codementor.io/ziad-saab/let-s-code-a-web-server-from-scratch-with-nodejs-streams-h4uc9utji)
* [**PHP**: *Writing a webserver in pure PHP*](http://station.clancats.com/writing-a-webserver-in-pure-php/)
* [**Python**: *A Simple Web Server*](http://aosabook.org/en/500L/a-simple-web-server.html)
* [**Python**: *Let’s Build A Web Server.*](https://ruslanspivak.com/lsbaws-part1/)
* [**Python**: *Web application from scratch*](https://defn.io/2018/02/25/web-app-from-scratch-01/)
* [**Python**: *Building a basic HTTP Server from scratch in Python*](http://joaoventura.net/blog/2017/python-webserver/)
* [**Ruby**: *Building a simple websockets server from scratch in Ruby*](http://blog.honeybadger.io/building-a-simple-websockets-server-from-scratch-in-ruby/)
* [**C++**: *Build your own VR headset for $100*](https://github.com/relativty/Relativ)
* [**C++**: *How to write an emulator (CHIP-8 interpreter)*](http://www.multigesture.net/articles/how-to-write-an-emulator-chip-8-interpreter/)
* [**C++**: *Writing a Linux Debugger*](https://blog.tartanllama.xyz/writing-a-linux-debugger-setup/)
* [**C++**: *How a 64k intro is made*](http://www.lofibucket.com/articles/64k_intro.html)
* [**Go**: *Build a web application in Go*](https://www.sohamkamani.com/blog/2017/09/13/how-to-build-a-web-application-in-golang/)
* [**Java**: *Build a Flashlight App*](https://www.youtube.com/watch?v=dhWL4DC7Krs) [video]
* [**JavaScript**: *Learn JavaScript Promises by Building a Promise from Scratch*](https://levelup.gitconnected.com/understand-javascript-promises-by-building-a-promise-from-scratch-84c0fd855720)
* [**Python**: *How to Build a Kick-Ass Mobile Document Scanner in Just 5 Minutes*](https://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/)
* [**Python**: *Building a Facial Recognition Pipeline with Deep Learning in Tensorflow*](https://hackernoon.com/building-a-facial-recognition-pipeline-with-deep-learning-in-tensorflow-66e7645015b8)
* [**Python**: *Recommender Systems in Python: Beginner Tutorial*](https://www.datacamp.com/community/tutorials/recommender-systems-python)
* [**Ruby**: *A Pedometer in the Real World*](http://aosabook.org/en/500L/a-pedometer-in-the-real-world.html)
* [**Rust**: *Let's build a browser engine*](https://limpet.net/mbrubeck/2014/08/08/toy-layout-engine-1.html)
To the extent possible under law, [Daniel Stefanovic](http://twitter.com/danistefanovic) has waived all copyright and related or neighboring rights to this work.
