So, something about the current version is completely broken.
I made it to infinity on insane with merely Y-unit attack per second.
All I did was have most things maxed out (including up to tier-2 upgrades, but Warp defense was not maxed out)
Warp defense might be broken. I've been leaving the game on Easy and haven't touched upgrades since wave 15000, now at 21000.
The void is making sure that I only need logarithmically more fire power per enemy health, but since enemy health increases exponentially, I need linearly more fire power.
But now, everything either instantly dies or is blown away. The only stuff left are the bosses, and they've hit me well enough time that I should have been killed by them. But warping defense is capped at 80%, and every single time a boss hits my tower, it's warped away. It's as if the code made it 100%. And I know that all of the absorb/survive/warp upgrades add up to a 1/200 chance of dying given an instant kill shot, but the boss character is definitely warping back, not sticking to the tower.
It would likely be a more strategic game if life regeneration was not broken; with life-regen coming from Nature and Life Drain, and perhaps some small amount from % regen per second, getting one-shot becomes the only way to die, which is why bosses are the bottleneck.
Element's relative defenses are broken. Getting it to 99%, or merely from 90 to 99% results in a huge difference which is certain to make you immune to all attacks for a little while. This also makes white enemies incredibly strong as opposed to all others, but fortunately they are not common.
Boss monsters are a bottleneck for HP, since it ultimately comes down to whether they can one-shot you or not. Multishot is equivalent to bouncing, except it's more reliable and easier to hack in since laboratory allows for it to reach 12 projectiles quite easily, whereas bouncing 10 times is almost impossble with % bounce less than 60.
You could significantly boost the performance of the game by making the quadratic leap of the coins into a formula that reacts to the time elapsed since the coin was thrown; this would be rendered by the GPU, thus there would be no difference in performance between a laying coin and a flying one. You wouldn't have to calculate the trajectory of each individual coin, that is.
I also recommend you revise your probability function; you probably bring back the coins that are out-of-bands on the exterior edge. This makes the coin concentrate on the lateral edges of the box. Consider adding perhaps a mod+factor into the formula to give an illusion of fair distribution.
HAaaaa ... Beat level 4 ... Jesus. This is heavy rote learning here. T'was almost to the point where I'd close my eyes and try to get the timing right. The thing is, when "outside" circles, you travel at a slightly different speed, so even timing can be messed up
At around 300 of each item bought, the prices get reversed; the oil rig is the least expansive (except for lemon stands) and the journal is the most expansive. This doesn't quite make sense.
It also seems that putting giving the same value to boxes magnifies the pattern, so 0 0 0 0 120 makes a small triangle, but 120 120 120 120 120 makes a large triangle...
I just realized the numbers we put in are the amount of degrees per frame that the sticks rotate... So 360 = 0, and 180 draws a line, etc. Similarly, 120 draws a triangle in 3 frames, and 121 or 119 draws a triangle that rotates on itself...
Another tip, if I may, is to consider multiples of numbers. It seems that by making numbers with dissimilar multiples makes the shape repeat several times, and putting chaotically dissimilar like 27.15 and 86.99 will make shapes that take forever to draw. Although, a nice application to this is add 0,1 to any number of any simple shape to have it repeat several times.
David star! 121 119 121 119 360 ... If the 4 first values are near the internal angles of perfect shapes like triangles, squares, pentagones, etc. And that you insert the numbers like this, it will make a upside-down shape in that shape, like a david star...
 "The Perfect Tower"){kind=icon}
 "Idle Civilization"){kind=icon}
 "Coinbox TapTap"){kind=icon}
 "oO"){kind=icon}
 "AdVenture Capitalist"){kind=icon}
 "Anti-Idle: The Game"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "Balloon Invasion"){kind=icon}
 "Cursed Treasure: Don't Touch My Gems!"){kind=icon}
 "Rotatix"){kind=icon}
 "Qoosh"){kind=icon}
The coins are for the most part completely dead when lying on the ground. As for what else you mention... uh yea I can look into that..