Hearthpwn

Card by card:

Zombie Chow: Heal for 5 if you're low, also good for an ai dupe target as it heals you.

Doomsayer: Amazing board clear, works every time!

Explosive sheep: Play it and ping his, hopefully it will proc the dupe so the boss will play free board clears for you.

Mad Sci: Sounds crazy, but it is a mill tool and helps you get those secrets rolling. I want to say the boss is packing 6 secrets so this will really help mill, and you can usually proc the secrets in a way that is beneficial to you. 

Unstable Ghoul: 2 mana slow the zerg down. Basically 2 damage will wipe 1/2 or more of the board every time. 

Arcane int: Sometimes you need a better hand or another answer.

Coldlight: Mill and more cards for you! Try not to get this duplicated!

Frost Nova: Stall

Ice Barrier: Stall, and usually amazing for surviving the late game.

Ice Block: MVP

Twilight Flamecaller: It's a bit of an expensive aoe, but it also gives a decent body.

Fireball: End game... these go face

Cult Apothecary: When/if you get popped or low, use this to reload and not be dead. 

Blizzard: stall + aoe

Flamestrike: bigger aoe Kappa

Alex: Use at the very end to cut boss hp and finish the game.

Mulligan: Sci, sheep, doomsayer

Early game: You really really really really want mad scientist into sheep + ping sheep as it will typically proc dupe on sheep and win you the game on the spot. However, if you can't pull this combo off it's okay! Just clear off minions using pings, and remember that it's okay to ping minions down and take damage. 

Boards to clear: Spell damage boards #1 - arcane missiles hurt... a lot. Waker/mana wyrm boards #2 also an easy way to let the ai amass damage. If you're lower than 14 #3 just a safety precaution. 

Mid game: Establish dominance and keep that board clean! This is where you'll look to be efficient and maximize value while thinning the ai deck. If you can mill here, do it because the ai loves to draw cards even with a full hand.

Cards to be afraid of mid game: Rhonin - big, hard to kill and it gives a massive amount of damage to the ai especially with spellpower. Using one fireball on this guy feels bad, but it's okay, just try to fill the ai hand if you can first to avoid the SMOrc missiles. 

Late game: Last minute healing, maybe another board clear or two and this game should be in the bag! If you did your job well, the ai should be around 8-12 cards ahead in their deck by now, and fatigue should come soon. This is the time to play alex, and start going in for the kill with fireballs etc to face!