BTCS also had it's own programming language that allowed you to create different effects (and there are quite a lot of them). I've included three examples below in the pictures, including one that I created (because you can create them from scratch instead of using their examples). They are:
Breath Riddle: Create a riddle and get input from the player. If they answer correctly, do something (in this case, they are awarded a broadsword). If they answer incorrectly, do something else.
Pit: Tell the party they fell in a pit and damage them.
Spinning Combat: Here's the one I created. Tell the party it's dark. Make it dark. Spin them around. And then, attack them with a random combat just to confuse them even more. (I could have done a great many other things if I had wanted to, including teleport them).
This is just three examples of the tons of things you can do with their built in language. Not all effects are bad, either. You can heal the party, regenerate spells, give items, etc.
Again, I apologize for the small pic sizes. It's just how DOSBox captures them.