Levels 20, 30 and 40 are simply horrible, because of 2 major flaws in game design. Level 20, first, is very, VERY long, any error is incredibly punishing, and as there are luck-based obstacles (angle cannons), well... it's even more. Level 30's walktrough is basically doing a sacrifice to RNjesus, there is no way to control the outcome, simply go forward and pray. Even if you go to the tunnel, you can still die stupidly, because you can't stop running even if you are in a collision course with a saw. As far as I saw, level 40 has... both sins? And it also has some nearly-undodgeable rockets. Good graphics, dialogues but terrible level design. 2/5, would update to 5 if fixed.
Sometimes, the "destroy bad picks" button doesn't sells a pick being completely inferior to yours, both in term of damage and speed, because it has a very high quality.
Fact: protium is the name of the nucleus of hydrogen-1, and it is completely stable, making 99,5 percent of hydrogen (the rest is deuterium and a very tiny inch of tritium). It wouldn't be bad if it was a fusion reactor, but as it is a fission reactor, how about other superheavies like seaborgium? Why noy Flerovium? Livermorium? Dubnium? Copernicium? Ununoctium? By the way, if your goal was to refer to actual fusion, maybe "tritium" would be better.
Tip: 4 5th tier vents almost perfectly encase a seaborgium quad, it allows super-compact durable reactors. Simply place those crosses (4 vents, 1 4-S cell) everywhere, and use a fair number of capacitors to store/drain energy output.
And here's a little suggestion: achievements are sure helpful, but their goal is kind of repetitive. What about more achievements, like, as an example, AI-based ones? I'm thinking of the name: Holy: have 1000 AIs ; Angelic: have 1M AIs; heavenly: have 1B Ai; Godly: have 1T AIs. These wouldn't have to be earned again and again for obvious reasons, and would give you a little bonus: how about adding 5%/10%/15%/20% more power to AIs? (I mean, if one AI's power is 2%, then with the first it would become 2,1% and so on). It would make a total of 50%, which isn't enough to be unbalanced, but is enough to give the game a small kick.
summox: In fact, you shouldn't try to reach the second series of upgrades at the beginning. Soon, they will be far easier to reach, and eventually you'll buy them in less than a minute after you start.
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