itch.io

• As QoL, I'd add floating x10 (or x5) and x25 buying selectors (rounded square, green bg, black font) on the top of left column or beside it (below/horizontally or before/vertically ARENA xxx), an add that could be free or buyable with x diams.

• And if you have free time, a 2nd color scheme ^^ something like Dracula > https://github.com/dracula/dracula-theme

• The floor could change depending on arena level/skin unlocked ( I like what Jim selected for his Clickapocalypse 2 game

> tiles pack http://pousse.rapiere.free.fr/tome/

Creating lightweight patterns 

> https://www.transparenttextures.com/, https://jenniferbourn.com/background-pattern-generators/ (personal favorite: https://codepen.io/msurguy/pen/sbIio but idk how it'd be interprated in a pixellised context)

• If you plan to push the game way further, an optional scientfic notation (e^11 instead of Ud/Udc) could be a cool QoL add.
• New foes & skills (Hurricane Ninja => throwing thrice daggers, Sadist Dentist => skulls throwing teeth dealing zap+dagger damage)! and more Passive Income multipliers: x32 for 512 diams, x64 for 16384 diams etc. ;..;
• if you're patient enough, a side story describing Earls' universe, an anecdote for each foe - all of which should be re-readable in a popup centered above the arena or ot on the right side of it) triggered by a button ('H' for 'History) near the Settings, with or without limits ('no-limit History' could be a reward)

PS: thanks for the new skins! I'm now a Toxic Earl (idk when I've unlocked those, I've stopped tracking process 3 days ago)