Hi there. Maybe it's my first post in English (because i'm hoping that this post will be indexed by google robot.. hehe)
Well just straight ahead, i'll give you some hints in finding the Basic Level X Codes at HackThis!! that i had found last holiday.
However, i hope that you find this post useful after you've been stuck for a day, week, or maybe a year :D
(in other word, please TRY to figure it out by yourself FIRST, then look at hints on forum/internet or this post)
Here you go (hope that i still remembered :D)
First of all, there are 4 codes, 3 in the main site and 1 in the forum. I'll give you hint from which one i found earlier (the easier i think).
All the codes will be in this format >> blx_code: something_meaningful
1. This code is.. what to say... hidden but not really hidden :p
1.1. In the main site, you'll always found it, but you can't notice it
1.2. It's something like finding a piece of black hair in the dark
1.3. Final hint, the code is hidden somewhat like this (highlight this word pleasee) (or you can also inspect the page)
1.3+ This trick can be done by Ctrl+A in the page or Ctrl+F then search for blx_code in the page source
2. This code is.. like the description before :p
2.1. Well to find it, you need to find the 'secret door' first
2.2. The 'secret door' is something related with the site creator/owner
2.3. This 'door' is located in the place where you can see the bio of the people, the levels that this people has completed and some 'not important' stuffs
2.4. It's related with an animal (i have no idea for describing this clue -__- )
2.4. Final hint, do the same trick like before, or inspect the page :D
3. This code is.. the special one :/
3.1. It's the one that located in the forum
3.2. It's in the feature where you can go from a place to another, you will notice it
3.3. Final hint, instead 'jump' into the blx place, inspect it carefully..
4. This code is.. Stealthy enough!
4.1. It's on the place where you can see your progress
4.2. It's a vegetarian (wtf!?)
4.3. It's hiding under something that will change along with your levels completion progress
4.4. Final hint, do the same old trick, highlight or inspect the page
If you have found all the four, congratulation that you've finished the basic level X!!
Make sure that you've also finished all the fun levels at HackThis!!
P.S. Sorry for my bad english, i'm still learning, hehe :)