overthewire.org - Leviathan
I finished Leviathan
This is a 7 level wargame. The level which challenged me the most was level 2. Overall it took me about 2.5 hours to finish it.
It is a little bit harder than bandit, but it uses a lot of the same mechanics. The main difference is that there are no hints posted on the website. This makes it just a little bit harder.
A thing that helped me through a few levels was ltrace
I refrain from posting solutions, that would take the fun out of it. So go and try it out yourself.
Just log into leviathan.labs.overthewire.org with username leviathan0 and password leviathan0.
If you know of a cool wargame hit me up on Twitter.