Super Easy Hard Badge = Auto drive, Large wheels, Shark gun, As many upgrades as possible (I had maxed vehicle and combat upgrades but only level 3 general upgrade). Use spikes only when approaching the stack of grey boxes. After spikes run out, spam sharks as you approach the stack of grey boxes. Always try to get ammo from balloons and you'll never run out of sharks.
Finally got the hard badge after what seems like my 50th time playing this game! This game is so long that it deserves an extra medium or hard badge. But anyway thanks for the tons of fun, and my favourite is Links :)
I just want to add on to the top comments: 1. Don't wait until red has colonized a neutral sphere before sending out your nanos to recapture it, because by the time your nanos reach the sphere red would have multiplied and you would fail. Instead pay attention to where the red nanos are travelling and send out your nanos such that they will recapture the sphere right after red has just colonized it. 2. While red is busy capturing neutrals, use the opportunity to capture their weak spheres instead :D
I completed this game even before signing up a Kong account and loved it so much. This game was the reason I decided to sign up and start earning badges!
I may play other awesome games on this site but I will always come back and play this amazing game from time to time to re-experience nostalgia from this masterpiece!