i found a bug: when you reach the "down to dig" level and you jump over all the supposedly digging bricks and land only on the last one only this brick disapears but unit collision prevents you from going any further. of course i found that out on my first go and had to restart ^^ kudos, please fix it, i wasnt even able to make the bricks disappear when i walked over them after that very last disappeared first.
rush for hull integrity + nitro. as needed add fuel and drill strength. add the muel as soon as you make 300 a day without it and go straight for the lvl 2 muel. then rush for more hull integrity, fuel and drill strength. my route was at 1500 feet right before you hit the more stony rock area. i tried at my last die to go to 2300 feet and it worked much better (31 big whites instead of the usual 24) which gave me 31k instead of 25k. i had every depth achievement, and the money, blue diamond and white diamond collect achievement, though i only needed the white achievement to make it. i ended with 316k. good luck.
don upgrade dmg on slow towers, just fire rate, seems that is the thing that slows enemies, the amoung of getting hit without interrupt for too long. enemies start piling up and a nuke hits them all.
OMG, lost like 5 times for hard badge.
It's really easy if you use the map and build 20 slow towers (3 dmg, 2 rate) in the front with 4 nukes in the back, i got 1524 ^^
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