Glad you like it! :) The grappling hook can be used at specific spots where a white "!"-icon popps up. You have to press Q on your keyboard and select the grappling-hook from the menu to activate it. I have to admit it's a bit convoluted, but I'm working on a simpler solution for a future update :)
Have you set the "Battle Tutorial" option to ON? You should have gotten a tutorial on the action commands. Basically you have to hit enter as soon as the two circles overlap. Hope this helps!
You may need to fix the circle overlap thing because I'm able to get critical hits just by holding down enter, also when I attack the game lags and its hard to tell where the circle really is when I'm defending or attacking. I am not sure if its just my computer or if its the game so I figured I'd just let you know.
