Thanks for playing and thanks for the feedback!
I do not understand why I can select "nothing" in the loadout screen when starting a game
Why not? If the player wants to handicap themselves for an extra challenge, so be it.
The music is loud when starting the game. Can I change the audio volume in-game? How do I pause the game? 'P'? 'Esc'
Sorry, I haven't implemented those things yet.
Is the UI for alchemy slightly buggy? Should the top-most "water" peripheral one-sixth circle-piece bar be present?
Yes, that's intentional. What's happening there is that you're mixing water (blue) with larval excretion (green) to produce purifying wash (yellow,) a chemical that can only be produced through this chemical reaction.
Is there a way to quickly clear all ingredients/reset?
Yes. Pressing TAB will dump the entire mixture whereas right-clicking on a chemical will remove one instance of that particular chemical. For example: suppose your tank has 3x water. If you right-click on the water icon, the mixture will be reduced to 2x water; if you press tab, all the water will be immediately disposed of.
Now I died very quickly to exploding enemies in the first room.
An easy way to dispatch of them is to use frigor essence, i.e. the ice chemical. You can very easily freeze the mines, which inhibits their explosion attack.
I do not understand this game. A lot of it seems really polished and nice, but other parts seem only slightly polished or even confounding.
Apologies for the confusion, I didn't have time to implement tutorials and/or documentation so the game is very difficult to pick up right now. One of my main goals for the next DD is to implement a thorough tutorial to avoid further confusion.