Mercernaries vs. Gangsters, who will win? Choose your side and see who wins. You get new cards as you complete different map levels. Drag tower cards to where you want to place them. Click walking unit cards to send them out. To remove a card, drag the fire pot on it. S to sell a tower. Hints: Select your cards at the beginning of each game carefully, as they will determine whether you win or lose. Save up your money and then send out a large wave of units. Upgrade your towers whenever you can (you can only upgrade when you have an upgrade card.) Place your towers in key locations on the buildings to mount an effective defense against the enemy. Best Sky Scraper Defense games.