Thanks for playing and sharing your thoughts! Indeed this was aimed as a game-mode prototype for Demo Day. The way of pickups will have to be improved and I really liked your proposal of showing them as menu in Growth mode. I agree that lategame isn't well balanced and there's little I can do - the nature of Mutations and how they stack will always have player's power grow much more rapidly than enemies. I guess having a win-state is a must, otherwise I'd need to scale enemies unproportionally as well to end the game which will probably feel worse than allowing player to win. The thing I must do is to move the difficulty spike from the early game to later.

Performance improvement is a must for this game mode to work.

I have some ideas how I can spice this game mode up a bit:

• Make zooid counts limited by how many of them you have picked up. So you start with, let's say, 5 of each starting zooid available (also costing nutrition) and you can increase the limit by picking up the same zooid again and again. Zooid drops would make sense and stay important.
• Allow sacrificing zooids for Mutations or another zooid drops or just XP - allows you to clear your inventory of unused zooids

Raw notes from while I was watching the video. Some things you figured out later in the video, but I still note them - ideally they should be clear from the start:

• Enemies at the start don't let you figure things out - they could be passive until first level up
• Not clear what Grinder affects - would be useful to highlight zooids that other buffing zooids affect
• Not clear which pickups are shops and which ones are rewards for leveling up
• Not clear that level up awards appear in the center of the arena - could have a little zoom-out cinematic animation to show how they spawn the first time
• Survivors save file doesn't get deleted
• Starting Advena Layout is very non-optimal
• Shop tooltip could appear when you're over it to display what or why not you are getting the shop item
• Annoying to check Mutation rewards and keep off the fights at the same time 
• "I wish there was a way to prioritize which parts grow back" - parts grow back in the order they were grown. Re-placing parts (drag and drop in Growth mode) moves them back to the list. I should display the priority number, but it might too much for players to think of at the start. One of suggestions were allowing to keep snapshots of your layout for different occasions and allow switching through them. In your case swimming around with 2 movers and 5 structures only doesn't make much sense. You'd rather modify yourself to be faster or have more fighting power to defend yourself until you get back the lost nutrition and grow back to full form.
• Idea: dead zooid ghosts could display the order they're going to grow back at
• Game should display multiple tooltips if there are multiple things hovered - in rare cases it might happen in normal play, I think it should be good to have.
• Good idea to show Mutation selection in Growth mode!
• Highlight the zooids you are hovering Mutation for - as you've suggested, selection buttons in Growth mode would be easier to do for highlights.
• Note - you have been looking at stats on the left of the screen which didn't have Mutations applied. Should also display Mutation stats there
• More potent poison should change color - nice
• Your range could have been higher due to powerup.
• Self note: Enemies clump up too much - they are after action, might need to thing about some sort of disperse intention
• Squiter initial poison range is unproportionally too large compared to its projectile
• Powerup Addiction Agonizer or any other buffing zooid is pointless.
• Zooids should have their breed name somewhere written
• Game's dropping frames because something is "leaking" memory and makes physics raycasts more expensive. It's an old bug and I'm not sure if it's Unity's fault or not - in normal gameplay reloading scenes fixes this issue. In Survival mode you're always in the same scene, so the issue becomes more apparent. Also there are more enemies spawned as you play so the performance issue gets worse anyway - need to optimize AI to be less taxing in high numbers or overall.
• Need to explain Strain stat somewhere, maybe in sub-tooltips like card games do
• ESC should open the Menu to exit if it wasn't for the performance.

My lack of update notes on the itch page didn't indicate that I made some updates, so some things were already fixed before I watched your video:

• Level up rewards do not overlap for several level-ups
• When starting the Survivals you appear in the exact centre of the arena, preventing you from accidentally picking up starting Mutation

Some random balance ideas I had while watching the video:

• Radial restores 1 healing point on getting damaged
• Radial gets a speed buff on getting damaged
• Poison increases Melee damage dealt
• Flail carries buff effects!
• Mines carry buff effects and apply the m on explosion

Survivors improvements:

• Environment upgrade to spawn more environment Eggs
• Environment upgrade to increase the size of arena (and the radius of enemy spawners so they're more dispersed)
• Picking up already owned zooid pickups could give a random Mutation for the zooid