I'm happy to do any geometry or detailing gruntwork you need. I don't remember agreeing to write popfiles for this map, but I'm always happy to write an MVM popfile for anyone in need of one, so I have no doubt that I did agree, and I have no intention of refusing now.
But what I mainly have to offer is my thoughts, so here you go:
How I feel about the idea:
Converting Hydro to an MVM map is interesting, and will probably go over well in players' eyes, since Hydro is cool and people like to see it given a second chance at success. The idea of a 4-arena circular map with defender shortcuts and gates is also interesting - it doesn't feel like a 4-arena map to defend (no ridiculous walk times for defenders), but it maintains the ease of defending that a 4-arena map would have.
I think you would need to have very, very long waves to give the bots any chance of victory, so probably 4 or 6 waves instead of the 7 or 8 most people seem to prefer.
How I think it would play:
ARENA1 (Dam / Bot Spawn Area): Bots take after 1 strong subwave
ARENA2 (Power Plant / Gate 1): Bots take after 1 strong subwave if they already control ARENA1, gamestate soft resets when bots capture this due to gate capture properties, so defenders can push forward and keep holding this arena
ARENA3 (Warehouse / Gate 2): Bots take after 1 strong subwave if they already control ARENA2, gamestate soft resets when bots capture this
ARENA4 (Radar Dish / Hatch): Bots take after 1 strong subwave if they already control ARENA3
So, each wave where the bots could conceivably win would need to have at least 6 strong subwaves (first captures ARENA1, second captures ARENA2, third takes ARENA2, fourth captures ARENA3, fifth takes ARENA3, sixth captures ARENA4). Using this example from Dayal's steam guide, Bavarian Botbash only has a single wave with 6 subwaves, and I doubt they're all strong subwaves.
That's basically why I recommended long waves.
But, it also acts as food for thought with the map's design. Hydro's areas are all reasonably easy to hold, but if you intentionally made it so that ARENA1 and ARENA3 aren't holdable (e.g. rotating between routes takes way too long so bots will usually get past the defence), you could make it so that defenders will:
- Initially hold ARENA2 and lose it to one strong subwave
- Continue holding ARENA2 even after the gate is captured thanks to the gate stun, then lose it to one strong subwave
- When RED loses ARENA2, they should usually lose ARENA3 because they have to respawn and they can't try to hold ARENA3 for fear of the bomb slipping past them
- This means RED will have to hold ARENA4 and lose it to one strong subwave
- If you think that's too punishing, you could make ARENA3 not be a gate so RED can still try to shore up their defence by holding ARENA2 even if they get pushed all the way back to ARENA4
With this new structure, you could make a more "normal" MVM map/mission where three strong subwaves are capable of pulling out a victory for the bots, and if one subwave captures ARENA2, the bots have more chance of getting through with the parts of the wave that only have two strong subwaves in a row.
But I don't really prefer it, since only having one gate isn't conventional, and having incredibly long waves with some tough subwaves would be something really distinguishing and unique.
For instance, I don't even think a 9-subwave wave would be hard on this map as you originally proposed it, as long as it was broken up by some weak subwaves which give the defenders time to push forward before the tough robots spawn.
Here's how I basically think it'd go:
Subwave 1 (HARD): Takes ARENA1
Subwave 2 (HARD): Takes ARENA2, bots get forward spawn at ARENA2
Subwave 3 (HARD): Takes ARENA2
Subwave 4 (EASY): Defeated by defenders, defenders push forward and retake ARENA2
Subwave 5 (HARD): Takes ARENA2
Subwave 6 (HARD): Takes ARENA3, bots get forward spawn at ARENA3
Subwave 7 (HARD): Takes ARENA3
Subwave 8 (EASY): Defeated by defenders, defenders push forward and retake ARENA3
Subwave 9 (HARD): Takes ARENA3
Now, one more HARD subwave right after Subwave 9, and the defenders' geese would be cooked. Similarly, if the defenders ever failed to push forward after defeating an EASY subwave, they'd have a hard time fighting off the following HARD subwaves. But on the flipside, if the defenders occasionally managed to defeat a HARD subwave with minimal deaths, they'd temporarily keep hold of whatever area they're in, and only push forward if they aren't defeated by the next subwave. So it kinda of keeps the normal balance?
How I feel about the layout:
I think most of Hydro's arenas are good for MVM as-is. The connectors are worrying with their limited room to dodge robot attacks, but some of them are going to be one-way for defenders, and the other ones are only going to be used by defenders who are retreating anyway, so I think it's fine.
Usually, when modifying an official map, I recommend as few layout changes as possible, to avoid confusion from people who are familiar with the map. But Hydro is a special case, because very few people are familiar with it, and even the people who are familiar with the map tend to not really have a great mental picture of the connectors. So I think it's probably best to make the defender shortcuts as simple as possible - a relatively straight shot between the hatch and the gates, with an A and B sign above each one. For optimisation, you can make the tunnels dip down and then back up and use areaportals, so their straightness doesn't create a huge sightline that renders the entire gate area from the hatch area.
The shortcuts also introduce an interesting dynamic. The ARENA1 -> ARENA2 dynamic is just like a normal 2-arena MVM map (think Decoy) but a little harder for defenders - usually, on a 2-arena map, defenders only have to walk through 1 arena to get to the hatch, compared to the 2 they have to walk through to get to the bot spawn zone. But, with these shortcuts, defenders would have to walk through 1 arena (ARENA4) to get to the shortcuts, then one arena to get to the arena they desire. So it's easier for the bots to capture ARENA2 because of this.
I think to make it even more interesting you could remove the ARENA4 -> ARENA1 shortcut. That way, defenders have a 3-arena walk time to get to ARENA1, and a 2-arena walk time to get to ARENA2. But the bots only need to capture 2 arenas, so the probability that the first gate will be captured is high, and the game is less likely to just stagnate at ARENA1 like on Mannhattan, because if a defender ever dies, chances are they're not getting back to ARENA1 before the next subwave of bots has control of it. So defenders will usually end up actually having to retreat after losing a fight at ARENA1.
Removing that shortcut would also make navigation a lot simpler, because out of spawn defenders only have two options - go to capture point A, or go to capture point B.
Tanks and other minor stuff:
I feel like tanks wouldn't be a particularly worthwhile inclusion. They're a mechanic that usually force defenders to retreat - they artificially weaken the defense in the area they spawn in by forcing 2-3 defenders to focus on them, making it easier for the bots they spawn with to kill the other defenders.
But in this map there are already gates which will naturally move the defense back over time. Tanks just feel like something that would add more confusion on top of a map already jam-packed with decisions - for instance, after you spawn, do you go to A (ARENA2) to help your team in the fight, or do you go to B (ARENA3) in case they lose and you really need to stop the gatebots/bomb carrier? Now think about if there was a tank in play too. It rapidly becomes mindless chaos.
Potato/Sigmod stuff: Nice to have if you can set it up, but I personally probably wouldn't use it in my mission(s).
Forward upgrade stations: Yes. Plonk them down right in the middle of each arena and don't turn them off mid-wave. If I want to upgrade mid-wave, I don't want to also have to yell at my engineer to buy 2ways, or worse, yell at my teammates to switch to engineer.
Overarching theme for missions: Idk, probably has to do with pyrosharks and fire because haha funny water get it?? Vague industrial theming would also work, like engineer bots (battle or otherwise) and demomen themed as "pipelayers" or "metalworkers" or something
