i reached x220.9 research speed with no research to discover... some upgrade are just useless at a certain time...
rapid fire duration: i have it at 30 sec and increasing, with 100% of chance, it became redundant because the tower it's in permanent rapid fire
multishot and bounce: you can have 50% chance in early game, it could be funny for late game if the chance improve at 100%
reflect, absorb, defence: in late game they are useless just because the tower kill way faster than the spawn, in early game they gave low bonuses that you can never think of any use.
regeneration: it's too much expensive for the heal rate in early game and useless for late game
in late game i have a "bug" the tower life drop at minimum and regenerate constantly without being touched.
pay-to-win is the way for ppl to have more and faster than others, not just to win something: pay to have x3 multiplier that no-one else can have, pay for faster day to accelerate the income... it's not just support for dev, with golden suit i could think to support the dev and gain no bonus above anyone else... this is an idle with weekly upgrade, more and less, and the gap between the different "stand" it's becoming silly without thinking to spend money for more multiplier. I'm playing since the release of this game and i still go on, because for now it's fun, but i barely achieve 800 in everything and i have to wait days for a mere x10 in one of the lower "stand". I could accept this, it's an idle game after all, but the pay-to-multiply and the pay-to-accelerate, for me, it's a hoax to those who like the game and like to playing it.
there isn't any sense to cap Erana Wildfire skill because it is exactly the same skill of acid potion without the extra splash damage and you can compensate the few vunerability with other heroes. Hardcore Mode it's almost impossible, even with maxed heroes, you can't kill mobs due to low amount of money to buy more towers and heroes: at stage 2 i can buy a total of 5 tower and 4 heroes and mobs at half wave are too many for the heroes to kill them and to build up more money to buy even the 5th hero. I got all maxed heroes and i tried to use pure single damage (like Viking), pure splash damage (like Druid) or a mixed strategy but it won't work. That's frustrating and senseless.
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Regarding the Tower life glitch: Did you upgrade lifesteal or nature by any chance? Feel free to write me a direct message :)