Yeah, I'm currently working on a fix for the font and I will also make the game fullscreen.
You are close about the strength. When attacking with strength against another attacking card of anything other than strength, the other card will win because magic is considered to be long or medium ranged, while weapons such as swords and maces are short ranged. BUT when attacking with strength against a defending magic card, then if the defending card's power is less or equal to 4, the strength card will win.
I decided not to write this info inside the game because I want players to discover them by their own. So they can plan ahead when building their decks.