Easy as pie. Just stay all the way to the right, and only move if a laser is going to hit you. Afterwards, move right back to the corner. Rinse and repeat. You only have to jump over three or four horizontally-moving blocks to beat it.
The trick to the hard badge ("Be The Ball") is powerups; you don't even need maxed equipment. Use the Airboost and Power Swing off every tee, and the super stop to avoid overshooting the hole. You can get several holes-in-one with this method, which makes the speedrun goals much easier.
Tortoise Shield. That is the answer to all the problems people are having with the final boss. It's (relatively) cheap and allows you to take your time with the corner turrets then circle around the kraken basically ignoring the enemy shots.
There is a bug with the keys; I think it has to do with having too many in your inventory at once. Anyway, you can get to a place where you have picked up all 12 keys but only opened 11 chests and not have any more keys. Incredibly frustrating.
For the puzzles you have to select (click on) the pig you want to get the equipment (armor, flashlight, etc.). There is a note in the shop but it wasn't obvious enough.
You can upgrade and sell towers after the level is complete (before you click to see the score screen). This allows you to easily get the in-game achievements for fully upgrading each tower type.
Screw those challenges. Seriously, I've never run into something so infuriating. As other people have pointed out, there are several challenges where you can be 1-shot by many cards -- so you die over and over and over and over again.
About half-way through the game and the Antique Clock is by far the best special. Gives you two extra hits which usually kills anything, even a mob with a pet.
For the HARD badge (Professional Zombie Masseuse Badge): Beat the standard game to unlock "Zombie Mash" mode. Sit in the middle of the screen with your grab-arms extended, swing around in small circles as the waves come in. After four or five waves you will complete the badge. Easy!
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