2019/02/15: "CodinGame may be the correct way to enjoy battle with BOT (AI program)" I did. If you like, please read this as well.

You can develop a test-first development style using 25 programming languages.

A site where you can study programming in games (or "pseudo game development environment"). It supports 25 programming languages. Recommended for those who want to be able to use multiple languages. Coding and debugging is fun because the graphics of the game move when you run the test!
The programming languages used for the answer are C #, C ++, Java, Javascript, Python3, Bash, C, Clojure, Dart, F #, Go, Groovy, Haskell, Kotlin, Lua, ObjectiveC, OCaml, Pascal, Perl, PHP, Python2, You can freely choose from Ruby, Rust, Scala, Swift, VB.NET. You can also (repeatedly) challenge a problem once you have solved it in another language.
Keep in mind that the problems on this site are provided as puzzles and may not be the best for daily programming studies. The number of problems is not so many. If you want to use it as a programming drill, [[Codewars] A site where you can train from the basics of coding with a browser (vim can be used with a browser and it supports 32 programming languages. More than 4000 problems have been posted!)] I recommend (https://qiita.com/javacommons/items/7c473cda7825ab99e08c) (* but this is my personal opinion as of 02/14/2019 *).

** CodinGame is a code creation / debugging / test (provided by the problem creator) on the browser (even if your machine does not have a development environment). It can be executed with a single button click, and it has the feature that "the answer can be submitted when the correct answer is approved". (So, it's safe with Rakuchin. Also, Codewars is the same) **

1. PRACTICE screen on the Codin Game site

Go to https://www.codingame.com/training in your Mac / Linux / Windows web browser. First, sign up using your Google account. Click "SIGN UP" at the top right of the screen.

[Site description] Codin Game is a challenge-based training platform for programmers where you can improve your coding skills with fun exercises.

2. Sign up

3. Position the training to be done first

4. Check training information

5. Open the problem (THE DESCENT) screen

Click the THE DESCENT image from the list to jump to the problem description screen.

6. Do a coding test in the IDE (answer screen)

The programming languages used for the answer are C #, C ++, Java, Javascript, Python3, Bash, C, Clojure, Dart, F #, Go, Groovy, Haskell, Kotlin, Lua, ObjectiveC, OCaml, Pascal, Perl, PHP, Python2, Ruby. You can freely choose from, Rust, Scala, Swift, VB.NET.

7. Read the instructions (maybe you should look ahead at the code!)

8. View the initial source code of the code editor

This training describes the logic that is processed on the server side, but in the beginner's task, data is exchanged using "standard input" and "standard output". Debugging can be done by writing to standard error using printErr (X); (for Javascript).
On the 13th line, parseInt (readline ()) is called 8 times, and the height is entered in the variable called mountainH, but it is discarded. On the 19th line, print ('4'); unconditionally outputs 4 (which means the 5th).
This problem isn't that challenging (?), So I'll solve it to explain how to use the IDE.

9. Add and run debug statements (test fails because not solved)

You can check the output equivalent to the one displayed in the debug statement by scrolling the lower left pane upward. (It's just an explanation of how to use printErr ())

10. "Submit" when all the tests have passed!

Finally

The CodinGame site also has a multiplayer mode to compete with other users. Studying English and C #, C ++, Java, Javascript, Python3, Bash, C, Clojure, Dart, F #, Go, Groovy, Haskell, Kotlin, Lua, ObjectiveC, OCaml, Pascal, Perl, PHP, Python2, Ruby, Rust You can practice logic development in, Scala, Swift, VB.NET, so why not start your challenge in your favorite language?

You can also try a problem once solved in another programming language. To try again, go to https://www.codingame.com/training and follow the steps below to access the questions you have already answered.
I found this site by looking at articles on overseas sites for information on Javascript, but there are other contents I would like to introduce, so if I find something new about CodinGame, I will write another article!

2019/02/15: As I wrote at the beginning, ['CodinGame may be the correct way to enjoy battle with BOT (AI program)'](https://qiita.com/javacommons/items/ I wrote a new article called b178c924199d1a6d524d). If you like, please read this as well.

[JAVA] [Codin Game] A site where you can train from the basics of coding with a browser (You can learn using a pseudo game development environment. Answers can be written by selecting from 25 programming languages!)