Practical Guide
I love this game, but it is insane how much money they're trying to get people to spend to beat 1 level. Every other level is a nightmare level, which almost always requires you to use perks to beat it or you lose any buffs you've earned. They also do contests, so you can try to win perks, but they change the advertisement later, after you've spent money, to say it was just a qualifier and not the prize. Absolute scam. It's so frustrating I end up not playing for 6 months at a time.