* [**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)
* [**C++**: _Raycasting engine of Wolfenstein 3D_](http://lodev.org/cgtutor/raycasting.html)
* [**C# / TypeScript / JavaScript**: _Learning how to write a 3D soft engine from scratch in C#, TypeScript or JavaScript_](https://www.davrous.com/2013/06/13/tutorial-series-learning-how-to-write-a-3d-soft-engine-from-scratch-in-c-typescript-or-javascript/)
* [**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)
* [**C#**: _How to create a Dragon in Augmented Reality in Unity ARCore_](https://fr-film.net/v-how-to-create-a-dragon-in-augmented-reality-in-unity-arcore-tutorial-qTSDPkPyPqs.html) [video]
* [**C#**: _How to Augmented Reality AR Tutorial: ARKit Portal to the Upside Down_](https://www.youtube.com/watch?v=Z5AmqMuNi08) [video]
* [**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)
* [**Go**: _Building Blockchain in Go_](https://jeiwan.cc/posts/building-blockchain-in-go-part-1/)
* [**Go**: _Code your own blockchain in less than 200 lines of Go_](https://medium.com/@mycoralhealth/code-your-own-blockchain-in-less-than-200-lines-of-go-e296282bcffc)
* [**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)
* [**JavaScript**: _How To Launch Your Own Production-Ready Cryptocurrency_](https://hackernoon.com/how-to-launch-your-own-production-ready-cryptocurrency-ab97cb773371)
* [**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)
* [**Python**: _Building an automated Cryptocurrency trading bot with Python on Binance_](https://www.youtube.com/playlist?list=PLIFBTFgFpoJ-2Qq6GFW-knNyAR9PcOwPw) [video]
* [**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**: _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**: _Chatbot Fundamentals: An interactive guide to writing bots in Python_](https://apps.worldwritable.com/tutorials/chatbot/)
* [**Python**: _Step-by-Step Instructions for Building a Basic Facebook Chat Bot_](https://blog.hartleybrody.com/fb-messenger-bot/)
* [**Python**: _How to Build Your First Slack Bot with Python_](https://www.fullstackpython.com/blog/build-first-slack-bot-python.html)
* [**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)
* [**Python**: _Creating Reddit Bot with Python & PRAW_](https://www.youtube.com/playlist?list=PLIFBTFgFpoJ9vmYYlfxRFV6U_XhG-4fpP) [video]
* [**R**: _Build A Cryptocurrency Trading Bot with R_](https://towardsdatascience.com/build-a-cryptocurrency-trading-bot-with-r-1445c429e1b1)
* [**Crystal**: _Why you should build your own NoSQL Database_](https://medium.com/@marceloboeira/why-you-should-build-your-own-nosql-database-9bbba42039f5)
* [**JavaScript**: _Dagoba: an in-memory graph database_](http://aosabook.org/en/500L/dagoba-an-in-memory-graph-database.html)
* [**Python**: _DBDB: Dog Bed Database_](http://aosabook.org/en/500L/dbdb-dog-bed-database.html)
* [**C++**: _Emulation tutorial (Master System emulator)_](http://www.codeslinger.co.uk/pages/projects/mastersystem/memory.html)
* [**JavaScript**: _GameBoy Emulation in JavaScript_](http://imrannazar.com/GameBoy-Emulation-in-JavaScript)
* [**Python**: _Emulation Basics: Write your own Chip 8 Emulator/Interpreter_](http://omokute.blogspot.com.br/2012/06/emulation-basics-write-your-own-chip-8.html)
* [**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**: _Gooact: React in 160 lines of JavaScript_](https://medium.com/@sweetpalma/gooact-react-in-160-lines-of-javascript-44e0742ad60f)
* [**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)
* [**C++**: _Tetris tutorial in C++ platform independent focused in game logic for beginners_](http://javilop.com/gamedev/tetris-tutorial-in-c-platform-independent-focused-in-game-logic-for-beginners/)
* [**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)
* [**Python**: _A Neural Network in 11 lines of Python_](https://iamtrask.github.io/2015/07/12/basic-python-network/)
* [**C**: _Kernel 101 – Let’s write a Kernel_](https://arjunsreedharan.org/post/82710718100/kernel-101-lets-write-a-kernel)
* [**C**: _Kernel 201 – Let’s write a Kernel with keyboard and screen support_](https://arjunsreedharan.org/post/99370248137/kernel-201-lets-write-a-kernel-with-keyboard)
* [**JavaScript**: _Build your own basic physics engine in JavaScript_](https://www.graphitedigital.com/blog/build-your-own-basic-physics-engine-in-javascript)
* [**PHP**: _Code a Search Engine in PHP_](https://boyter.org/2013/01/code-for-a-search-engine-in-php-part-1/)
* [**Ruby**: _Write an Internet search engine with 200 lines of Ruby code_](https://blog.saush.com/2009/03/17/write-an-internet-search-engine-with-200-lines-of-ruby-code/)
* [**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**: _Building a software and hardware stack for a simple computer from scratch_](https://www.youtube.com/watch?v=ZjwvMcP3Nf0&list=PLU94OURih-CiP4WxKSMt3UcwMSDM3aTtX) [video]
* [**C**: _How to Write a Video Player in Less Than 1000 Lines_](http://dranger.com/ffmpeg/ffmpeg.html)
* [**C**: _Learn how to write a hash table in C_](https://github.com/jamesroutley/write-a-hash-table)
* [**C**: _Writing an SVG Library_](http://www.code-in-c.com/writing-svg-library-c/)
* [**C**: _The very basics of a terminal emulator_](https://www.uninformativ.de/blog/postings/2018-02-24/0/POSTING-en.html)
* [**C++**: _Build your own VR headset for $100_](https://github.com/relativty/Relativ)
* [**C++**: _How X Window Managers work and how to write one_](https://seasonofcode.com/posts/how-x-window-managers-work-and-how-to-write-one-part-i.html)
* [**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)
* [**C#**: _C# Networking: Create a TCP chater server, TCP games, UDP Pong and more_](https://16bpp.net/tutorials/csharp-networking)
* [**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)
* [**JavaScript**: _Implementing promises from scratch (TDD way)_](https://www.mauriciopoppe.com/notes/computer-science/computation/promises/)
* [**Nim**: _Writing a DMIDecode Parser_](https://xmonader.github.io/nimdays/day1_dmidecode.html#cid1)
* [**Nim**: _Writing a INI Parser_](https://xmonader.github.io/nimdays/day5_iniparser.html#cid13)
* [**Nim**: _Writing a Link Checker_](https://xmonader.github.io/nimdays/day4_asynclinkschecker.html#cid10)
* [**Nim**: _Writing a stow alternative to manage dotfiles_](https://xmonader.github.io/nimdays/day6_nistow.html#cid16)
* [**Nim**: _Writing a URL Shortening Service_](https://xmonader.github.io/nimdays/day7_shorturl.html#cid20)
* [**Node.js**: _Build a static site generator in 40 lines with Node.js_](https://medium.com/douglas-matoso-english/build-static-site-generator-nodejs-8969ebe34b22)
* [**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)
* [**Python**: _Write SMS-spam detector with Scikit-learn_](https://medium.com/@kopilov.vlad/detect-sms-spam-in-kaggle-with-scikit-learn-5f6afa7a3ca2)
* [**Python**: _A Simple Content-Based Recommendation Engine in Python_](http://blog.untrod.com/2016/06/simple-similar-products-recommendation-engine-in-python.html)
* [**Ruby**: _A Pedometer in the Real World_](http://aosabook.org/en/500L/a-pedometer-in-the-real-world.html)
* [**Ruby**: _Writing a CI Server_](https://developer.github.com/v3/guides/building-a-ci-server/)
To the extent possible under law, [Daniel Stefanovic](http://twitter.com/danistefanovic) has waived all copyright and related or neighboring rights to this work.
