Difficult quest for habravchan: 25 levels

Hello everyone, my name is Vlad, I am a programmer at Mail.Ru Group. In 2010, I did a quest for habrayuzerov and it was more than 10 thousand people. For this day I decided to do something similar to the programmer, but I didn’t have time to do it a bit: I complicated the quest and could not stop. (-:



Solve the puzzle here: puzzle.mail.ru

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Prizes! To the first person who will answer all 25 questions, we will present the Raspberry Pi 3 from the DIY community of Mail.Ru Group. There is also an intermediate prize: the one who passes the 15th level first will receive an invite from me on Habr.



How to proceed:



- Login and password during registration are needed to continue the game on another computer;

- The puzzle consists of 25 levels. At each level, it is necessary to find out (find or calculate) the secret word and enter it in the input field at the top;

- Often there are clues at the level, but sometimes the other way around is superfluous distracting information. Tips are often hidden. Do not forget to look into the HTML-code of the page;

- To pass the game you need a basic knowledge of web-technologies, computer science, to know what ASCII, RGB and the number system are. In principle, it is not necessary to be a programmer. (-:

- On a mobile or tablet is unlikely to pass, because you will most likely need some kind of text and image editor.

- All tasks can be solved "on a piece of paper" without programming, but, of course, no one forbids solving using the program.



Ask questions in the comments. Belatedly congratulations to all involved in the programmer's day!



UPD:

1) There is no error in the 6th task! Carefully study the condition.

2) In the 24th there was a mistake in the condition, it is fixed.



UPD2:

Invite left DeniSix in the 38th minute.

Raspbery Pi gets Dr_XaoS (time 1:37).

All the rest are automatically added to the board of honor!