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In my opinion, this game shouldn't be severe for newcomers.
So, renting an upgrade may be good.
For example, a newcomer heard that "'Hardened' is very good upgrade. If you use Acorn, you must equip it." So he rents that upgrade for a month by spending 200,000 coins.
Or, a player wants to test Shogun-guard before purchasing for rainbow-stars. So he rents that upgrade for a month by spending 1,000,000 coins.
Or, a veteran wants to play with new Legendary upgrade of this month (Steam Blaster) before getting and spending bulbs. So he rents that upgrade for a month by spending 5,000,000 coins.
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In another thread, I posted a comment like above (but no reply).
And, in my opinion, renting a costume that is in current shop for 24 hours may also be good.
Borrowers will remain in Pvp area for a long time in that day to test and boast that costume, so number of joining players will increase.
And non-borrowers can watch that funny costume many times.
(And, after Rux stops selling and lending it, buyers will be the only players who can equip and boast it because borrowers will lose that costume).