Yay, the card worked for me this time. Note that if you won the card, it will show you regular "you won the card" message in the chat right away (you do not have to refresh the page as the description might make you think).
Finally, I figured it out. It'd help if the game was actually well-documented. The secret is that if you launch a missile at an enemy who is too close to the launcher, the launcher will be hit by the explosion and will blow up, giving you a game over. Too bad the instructions don't mention that.
It's a pretty good game overall. The battle system is good for what it is, but the dungeon-crawling screen is a bit plain. Overall, the game could use much more polish, too. Good attempt. 3/5