STAGE 1
Show yourself to everyone!


STAGE 2
Become a star!


STAGE 3
Final step to the pantheon


You will get each of these for completing ARENA I, ARENA II and ARENA III respectively. There are some tips for completing these in the section below.

Giant killer
"I don't care if you are ten metres high. I will kill you anyway!"


I personally got this after beating ARENA I. I feel like you get it for beating any boss at wave 10 in any mode.

Armorer
Every weapon is important!


Save up and buy all weapons at an overall cost of $22,000. This is probably easiest achieved in the survival mode, since there's no limit on time or number of waves.

Mega mex
"Huge robots are the best."


For this you need to repair the Upgrade Machine, then purchase the mech and its two upgrades. This can only be done in the survival mode.

Wall builder
Defense should be the best!


To get this, you have to fully upgrade one wall. This can be done in any mode.

Cool guy
"Cool guys don't look at explosion."


You can repair the Mass Attacks station for $2,000. After purchasing one of the available attacks, use it by clicking on it at the top of the screen and clicking somewhere on the battlefield. You will get this when you use an attack.

Full pockets
...


During the survival mode, there will be waves where a progress bar is shown and there is a constant stream of enemies until many have been taken out. When this wave is complete, the last enemy defeated will drop an item with a useful effect.
You can get this achievement by collecting three of these items in one session.

Magnate
...just business.


You will get this for building up $50,000 in spending cash. It must be money currently in hand, so it doesn't include money you have spent on upgrades.

The reason for this guide is due to the three arena stages being puzzles more than unique stages. You get a limited amount of money and specific enemies to fight that will crush you if you don't choose wisely at the start. The following information is what I did to beat all three stages.

To get the three other achievements, beat the first arena boss, buy all weapons in one game, and fully upgrade a wall in one game. The all weapons and wall can be done in one go while doing Arena 3 or through Survival.

Rule no. 1 with all arena modes: Always kill them near the light/security cameras. The audience hates offscreen killing so much, they won't pay you for it. The monster needs to be up to 10 player models away on kill to get the money. This even applies to flying monsters.

Arena 1: Buy the SMG (The one that cost $1000), Rocket Boots (The one that enables you to fly for short bursts), and Double Life. Buy the upgrades in that order. You can beat this arena just from buying walls and lower turrets but will make beating the boss harder since the turrets don't shoot at the boss. Upper turrets won't hit the minions, making them useless.

Arena 2: Fun fact: you don't really need the Rocket Boots until wave 5-6. Buy the SMG, then buy all the turrets. Buy the Rocket Boots when you feel like it because the enemy is only attacking you, not your reactor. Actual defensive tactics need not apply this arena :) This level requires the most player skill to avoid flying enemies.

Buy the Grenade Launcher and use it for the boss. It's a useful gun throughout this Arena, so consider buying it as soon as possible, but it's not mandatory until the boss. The grenade splash will help a lot in regards to killing the mini seeking missiles the boss shoots out.


Arena 3: Buy the Flame Thrower and save the rest of the money until Grenade Launcher. It takes 1.5 ammo clips worth of Flame Thrower to kill a golem and they wreck shop on the Reactor so hard, that just one can destroy it within 6 seconds.

For some reason I don't understand, the Siege Bugs that shoot a volley of projectiles either do very little or no damage to the Reactor, so focus entirely on killing the golems first before taking out the Siege Bugs. I recommend starting a wave, then running over to one side and unload a full clip on the golems, follow by running to the other side and killing those golems outright. The timing should be such that you'll get paid for the golems that you killed on the other side, but I might be off a few seconds. Either way, use that game plan and you should get enough money for Grenade Launcher on wave 6.

Buy a Wall after wave 6 and fully upgrade that one as you go. Get Rocket Boots and Double Life to make your life easier when helping your wall. You'll have so much money before the boss, you can fully upgrade two walls if desired. The boss is a very basic enemy that springs up from the ground and leaves a very noticable fissure in the ground before popping up. Avoid that and he'll be dead after 2 minutes of using the Grenade Launcher.

And that's it. Good luck on your Chieving ventures.