Today I'll give you a Walkthrough for Whiteboard Tower Defense which will give you the Hard and the Easy badges, I'm not sure about the medium, though. If you need help click the links, which are images, I would recommend you to see all of the images.
Obvious steps: Go to "Play" and click "50 Hard Levels".
Level 0: Make a few Peon Towers at the left.
Level 1: Make 2 more at the side.
Level 2: Build 2 Peon Towers below the previous ones.
Level 3: Build 2 more.
Level 4: Make 4 more of them like in the image.
Level 5: Build 2 more like in the image.
Level 6: Build 2 above the previous.
Badge acquired! Marker Sniffer Badge (easy – 5 points)
Level 7: While you're doing the level, build 2 more Peon Towers like in the image.
Level 8: Make 7 of them at the right of the previous ones.
Level 9: Build 4 Peon Towers like in the image.
Level 10: Make 1 above and 3 at the right side leaving a bit of space between them.
Level 11: Make 6 more of these towers below, put the last 1 a bit to the left.
Level 12: Make 16 Peon Towers and place them like in the image.
Level 13: Make more and put them as you see in the image.
Level 14: Change the place of the previous ones and put some new ones.
Level 15: Take the middle Peon Tower out and put a Stick Man in its place.
Level 16: Make 3 Stick Men and place them like in the image.
My tactic to prevent monsters from getting to your base: When they get to the last column, take the last Peon Tower out from below to the right and make a new one on the top right, as you see in the image.
Level 17: Build as you see in the image.
Level 18: Do the tactic, and then build a Stick Man.
Level 19: Make more Stic Men.
Level 20: Build 8 more.
Level 21: Make even more of them.
Level 22: Get some Peon Towers out and put more Stic Men.
Level 23: Make more of them.
Level 24: Flood the screen full of Stick Men after having beat the boss.
Level 25: Build more of these and place them like in the image.
Level 26: Make more Stick Men.
Level 27: At the moment, you should have all the towers as Stick Men, except 1, which is the one that isn't supposed to be a Stick Man because of the tactic.
Level 28: Upgrade Stick Men.
Level 29: Upgrade more.
Level 30: You should have all your Stick Men at level 2 now, so start to upgrade some to level 3.
Level 31: Upgrade the center ones.
Level 32: Take the middle Stick Man out, and put a Boss Tower. Upgrade a few Stick Men.
Level 33: If you have lag, like I've had, maybe 1 or 2 can enter your base. Make loads of Electric Floors.
Level 34: Save up money to be able to buy a Boss Tower the next level.
Level 35: Make 2 Boss Towers in the middle.
Level 36: Make more of these.
Level 37: Upgrade your central Boss Tower and upgrade a few Stick Men.
Level 38: Upgrade another Boss Tower, after that upgrade Stick Men and also Electric Floors.
Level 39: Upgrade a Boss Tower and also Stick Men.
Level 40: Upgrade Boss Towers and some Stick Men.
Level 41: Upgrade a fe Stick Men.
Level 42: Get some more Stick Men upgraded.
Level 43: Upgrade Stick Men, now they're all level 3. Upgrade Electric Floors too.
Level 44: Upgrade a few Boss Towers and build 1.
Level 45: Get some Boss Towers upgraded and make 1.
Level 46: Upgrade a few Boss Towers and make 1.
Level 47: Save money.
Level 48: Upgrade the middle Boss Tower to red level. Save money.
Level 49: Get a Boss Tower upgraded.
Level 50: There's no need to do anything.
Badge acquired! Teflon Terrorist Badge (hard – 30 points)
Now you have 2 badges more!