Some tips if you want to beat the game in less then 5 hours

[marklar]

Using this method I was able to get all the achievements (except the Play for 5 hours one) in 3.5 hours, you can do it faster since I figured it out after about 5k kills.(I used a build based on maxing out damage, speed, health and regen untill that point, no abilities at all)

Start off the game upgrading your Damage to the max, don't worry about survival this early just try to kill as many enemies as you can and collect DNA. After maxing out your Damage, start upgrading your speed and health to kill enemies and inflict damage even faster.

After you have about 20 upgrade points( maxed out Damage, and 5 points in Speed, 5 In health) you should refund your points and max out: Ability Cooldown and Blast Power and make sure you chose the "blast now deal small damage" perk as this one is the most important part of the strategy.

Now all you have to do is lightly hit the Space bar to use the ability as fast as possible, holding the space bar is not recommended as you waste time and deal less DPS.
(It's important to note that when you damage enemies using the blast ability it doesn't count toward Inflict X total pain achievement, so you will need to bump into enemies occasionally.)
Afterwards you should max out blast radius, and health+ health regeneration to survive long enough for the 500+ kills in one game Achievement.

You should check the Stats screen in the main menu from time to time and if you see that you killed significantly more enemies then total pain inflicted, you sould stop using your Blast entierly and just bump into your enemies with max damage untill the ratio is about 1:100.

All that's left to do is leave the game running in the menu for the 5 hour achievement to pop.
Good luck!

[TreeTrunk]

Yes, very helpful, thanks