Close single-tile vehicle used as difficult terrain exploit.

[kevingranade]

Game version:
since addition of single-tile vehicles.
Operating system:
All
Tiles or curses:
Both
Mods active:
Any

Expected behavior

Interposing a single-tile vehicle between yourself and an enemy presents a flimsy and unreliable defense.

Actual behavior

Interposing a single-tile vehicle between yourself and an enemy presents a large and consistent defense because the enemy tends to attept to enter the square with the vehicle and takes a very large move penalty to do so, and the technique can be repeated indefinitely because there is no risk to the vehicle or it's contents.

Steps to reproduce the behavior

Acquire a shopping cart and a melee weapon.
Find a zombie.
Maneuver the cart between yourself and the zombie.
Repeatedly attack the zombie when it steps onto the cart.

[kevingranade]

Potential solutions:

• Mark most vehicle parts with cargo capacity as obstacles. (#22791 but applied to more parts)
  This addresses the issue for many common vehicles, but doesn't prevent you from making a "frame on wheels" that can be used just for kiting.
  It also ends up having impacts on unrelated vehicles like car trunks, where it is reasonable to climb into the vehicle via a cargo space.
• Characterize vehicles as "unstable", and change how they are interacted with.
  • Allow unstable vehicles to be "knocked over" by monster attacks.
    This might lead to a rather complicated system that offers minimal benefit.
  • Prevent boarding of unstable vehicles.
    This specifically targets the problem vehicles without disrupting anything else.
• Enhance even the dumbest monsters to path around obviously bad choices.
  This is pretty promising, a vehicle-scale obstacle is definitely an obvious enough for a zombie to notice for the same reason noticing it is impassible would be reasonable, and it only requires the monster to path by a single tile for it to be effective.
• fix handling characteristics for improvised vehicles. Shopping cart casters are nearly unusable on anything except hard, flat surfaces, especially if the vehicle is loaded.
  This is more a fix to the prevalence of shopping carts, you can just upgrade your way out of it with better wheels or a better cart so it doesn't fully address this issue.

[Nhatorama]

Not sure if this falls under:

rather complicated system that offers minimal benefit

Anything with a capacity less than a trunk's would have a 1 in # chances of giving the zombie/monster/NPC stepping on it its respective movement penalty (brainlessly crashes against it). So long as the entity stepping on the shopping cart doesn't make a bad roll, they don't get a movement penalty and the dumb 1 in # does.

A sort of:

Enhance even the dumbest monsters to path around obviously bad choices.

[kevingranade]

More suggestions from the forums https://discourse.cataclysmdda.org/t/goodbye-to-op-shopping-carts/14851/18

• Increase the time it takes to drag a cart that has a monster in it, and move the monster with the cart. Currently, dragging seems to entirely ignore monsters on the dragged vehicle.

• Have zombies sometimes smash small vehicles, instead of boarding them. Zombies already sometimes smash terrain instead of moving onto it, but arbitrarily don’t do the same to vehicles.

• Have zombies sometimes shove small vehicles out of the way instead of boarding them. I’m hesitant to suggest this because I think in most situations it won’t make much difference, but maybe I’m wrong.

• Add a time cost to 'G’rabbing and possibly releasing vehicles, as there currently is no cost. Then, either add ways to lose your grip or incentives to intentionally release it.

(My thoughts on these suggestions)
The fact that monsters don't currently board vehicles and move along with them is a major problem that needs to be fixed regardless of this issue.

Zombies randomly smashing at vehicles instead of boarding them is reasonable, but it doesn't fix the underlying issue.

Having zombies grab and shove vehicles would certainly add to the chaos, not totally sure if it helps reduce the immediate problem. What would help more is if the zombies pulled the vehicle away from the player instead of pushing it.

We could certainly add a grab cost, but it would be too trivial to matter. We don't generally base action durations on balance concerns, and i don't think we want to start here.

[Night-Pryanik]

We could also increase cost to attack with a weapon while grabbing. I think it's a lot harder (or maybe even impossible) to swing two-handed or heavy weapons with hand (or both hands) occupied by grabbing.

[Nhatorama]

Increase the time it takes to drag a cart that has a monster in it, and move the monster with the cart. Currently, dragging seems to entirely ignore monsters on the dragged vehicle.

It's strange that friendly (don't know if neutral/enemy NPC works the same) NPCs's weight that hop on your cart is calculated, but the enemies' isn't.

Have zombies sometimes smash small vehicles, instead of boarding them.

Have zombies sometimes shove small vehicles out of the way instead of boarding them.

IMO zombies' mechanics are fine as is (maybe slightly more buffed than what I imagine a zombie to be able to do) and I think the solution lies on the player's mechanics side and not on the zombie side (see my suggestion at the bottom).
I do find that The Walking Dead's interpretation of zombies behavior is spot on. A zombie's primary goal is to chew on non-tainted meat and anything else is irrelevant. The only reason a zombie would start pushing (or in CDDA's case hitting/smashing something) against an obstacle, is if said obstacle is entirely blocking any path to their target.

Having zombies grab and shove vehicles would certainly add to the chaos, not totally sure if it helps reduce the immediate problem. What would help more is if the zombies pulled the vehicle away from the player instead of pushing it.

I think this would be too much of a buff (increasing their intelligence) for zombies, but if it was added to Grabber Zombies I wouldn't mind.

We could also increase cost to attack with a weapon while grabbing. I think it's a lot harder (or maybe even impossible) to swing two-handed or heavy weapons with hand (or both hands) occupied by grabbing.

When I read this I thought "you can't hold/grab a two handed weapon/firearm and at the same time hold/grab a cart/vehicle (with both hands, unless you have extra limbs).", so how about requiring a player to be unarmed if they want to grab a cart/vehicle?

I guess you could argue that you can do this by using a hand to hold your 2 handed weapon and one hand to hold a cart/vehicle, but certainly you would be very slow at using and moving your weapon and cart respectively and if this was the solution used you should get pretty extreme penalties for trying to do both at the same time.

[BevapDin]

This is just a consequences of #11381 (monsters not boarding the vehicle). If they did, the player would drag the monster with them as the move away from it, which would make the the whole exploit vanish into a realistic scenario: the monster needs time to move on top of the vehicle, but once it's there, it moves along with the vehicle.

[GearheadLydia]

Though this is quite self-evidently a necessary improvement, I'm tempted to suggest tempering any possible fix with the potential to have a zombie (in effect) step on a wayward skateboard wrong and fall down comically - i.e., current behavior, but only applied to vehicles small enough that a zombie could fail to notice its presence.

Have zombies sometimes shove small vehicles out of the way instead of boarding them. I’m hesitant to suggest this because I think in most situations it won’t make much difference, but maybe I’m wrong.

This could get scary, in a good way - imagine a zombie flattening you with your own shopping cart.

Prevent boarding of unstable vehicles. This specifically targets the problem vehicles without disrupting anything else.

This seems sensible - the game already makes a distinction between the space inside a vehicle and the ground under it, right?