lol only idiot fanboys say anything can be hacked
it can't be. lots of things are so open that there's no hacking possible.
Adding onto what you say, here is why it is impossible to hack Blockland.
You have the client, and the server. The server keeps record with what is happening. The client just sees what happens. The server has variables for these players; where they are, what are they carrying, health, maxhealth, etc. A client can't edit these variables alone, only the server can. Now then, you may be wondering why you can press WSAD and move, that's because the command is sent the server in which the server will read the command and send you forward and play the walking animation. You don't directly change the position variable on the server. Same with items you have, health, maxhealth. Exploiting addons works because it tells the server to cheat, not because they haxed your norton.