Same time combat?

[ImthebOHGODBEES]

I've tried looking through this forum, Reddit, and general Google searches, but I can't seem to find any discussion about someone else trying this that I can reference and use as input.

I want to try and tweak 5e combat so that everything happens at once each round.

This is inspired by two things, really. The first is "Same Time Risk" as it existed in an old video game of Risk II. It really changed the way that combat occurred, but I thought it made it feel more...right?
The second is the strange shenanigans that happen when people basically take turns doing 6 seconds worth of actions. In theory it all happens at once, but in actuality you get a bunch of rubber banding and people moving strangely relative to each other, etc etc.

The way I see it working out is with the following changes:

Every "round" is only THREE seconds.
-This means that spells that normally last "until your next turn" last for two rounds when they work. maybe. Still figuring this out.

Everyone submits a basic description of what they want to do (the DM writes down for the NPCs).
-You can EITHER [attack/spell cast + move no more than 5 feet] OR [move + minor action]
-The submitted description is goal specific. You can move to a location, or towards a person, so that simultaneous movement means you are not moving towards where they were. You can even say "try to head them off" or "try to keep the pillar between us" or something.
-This allows for "held actions" as well like "If anyone comes into view I fire" or "if someone heals me I move over there"

All attacks/actions that can happen right now happen. Even if someone dies during this, they still pull off an attack/spell/action that falls in this category.
-So if it's ranged and you have LoS, boom attack. If it's melee and you're in melee, boom attack.
-If healing and attack both happen to the same person, you assume that both happen simultaneously and the end result number dictates what happens (unless the submitted action specifies)
--So if I'm at 10 hp, and Steve heals me and the goblin attacks me, if Steve heals for 10 and the goblin hits for 30, -10 means I collapse unconcious
--Unless Steve specified "I heal the idiot Barbarian after any damage is applied, in case he falls unconscious."

Then any movements that were submitted occur, any conditional movement descriptions taken into account.
-This is the part that I could see being trickiest, but it's also the part that feels most important to me.
-If the game is "theater of the mind" it's the easiest to just describe what happens.
-If the game is either online or in person with some sort of measured play space and character stand ins, the DM and the players can work out whether one person does all the moving or if everyone sort of works together to move their characters according to the stated intent.

Any triggered held actions occur that MIGHT mess with movement.
-In general I'd probably usually side with "Ok, you got the shot off, but the character's momentum carries them to the end of their movement" or whatever might apply.

Any other Actions/Attacks that need to happen now occur.
-This should basically be the clean up of held actions that didn't trigger or people that wanted to move and THEN minor (as specified in their submitted description).

Some things that I'm thinking would be vastly different or at least need to be figured out:
-How do BBEG's handle legendary actions?
-You can only attack/spell cast for X number of rounds in a row where X is your Con/Int modifier (minimum 1). This keeps people from going on a bender, and is more realistic. Gotta catch your breathe between sword swipes
-Initiative doesn't really come into this in any way. That may be good or bad.
-This makes some abilities/feats worthless while also opening up the floor for other homebrewed or house-ruled ones
-This may slow down the execution of a battle scene significantly, I have no idea
-Attacks of Opportunity aren't necessarily out the door, but I think it also opens up a lot of opportunities with "reactionary actions" like heading someone off at the pass, or shooting the one running away or something.

I admit this is a bit harebrained and I'm just curious what you guys think of it.
Like I said, one of my main motivators is the weird interactions that you see coming about because of the way initiative order ends up happening with movement.

[Greywander]

I feel like perhaps you're making this more complicated than it needs to be. If I wanted to do simultaneous turns, I would probably do something like the following:

• At the top of the round, each creature (PC and NPC) details how they use their Action, Bonus Action, and movement.
• Everything happens simultaneously, for example damage and healing are applied at the same time, with the final amount determining how many HP is left.
• To extend the above, healing a creature on the same turn that they drop to 0 has no effect, but a creature that takes both damage and healing while at 0 resets their death saving throws.
• Even if you drop to 0 HP, you still get to finish your turn. You drop at the end of the round. Status conditions are also applied at the end of the round.
• You can hold your action, which lets you use your Reaction to take an Action in the middle of the turn (after you find out what everyone else is doing).
• You can also use your Reaction to change your movement.
• If you move, you are considered to be in every location that you move through for the purposes of deciding if you are in range of an effect (attack, spell, etc.).
• Effects that force movement or slow or stop a creature take effect at a time chosen by the user of the effect while the target is in range.
• Extending the above, a creature will attempt to move to their original destination if they are moved or slowed during that round.
• If it is absolutely necessary to decide the order in which two creatures act, either roll initiative or simply let the highest initiative bonus go first (no roll needed).

Doing simultaneous turns in D&D is kind of messy and complicated. But not impossible.

[Grog Logs]

I think that there were 1-2 different UAs on alternative ways to do initiative that might fulfill some of your desires

[ImthebOHGODBEES]

I feel like perhaps you're making this more complicated than it needs to be. If I wanted to do simultaneous turns, I would probably do something like the following:

• At the top of the round, each creature (PC and NPC) details how they use their Action, Bonus Action, and movement.
• Everything happens simultaneously, for example damage and healing are applied at the same time, with the final amount determining how many HP is left.
• To extend the above, healing a creature on the same turn that they drop to 0 has no effect, but a creature that takes both damage and healing while at 0 resets their death saving throws.
• Even if you drop to 0 HP, you still get to finish your turn. You drop at the end of the round. Status conditions are also applied at the end of the round.
• You can hold your action, which lets you use your Reaction to take an Action in the middle of the turn (after you find out what everyone else is doing).
• You can also use your Reaction to change your movement.
• If you move, you are considered to be in every location that you move through for the purposes of deciding if you are in range of an effect (attack, spell, etc.).
• Effects that force movement or slow or stop a creature take effect at a time chosen by the user of the effect while the target is in range.
• Extending the above, a creature will attempt to move to their original destination if they are moved or slowed during that round.
• If it is absolutely necessary to decide the order in which two creatures act, either roll initiative or simply let the highest initiative bonus go first (no roll needed).

Doing simultaneous turns in D&D is kind of messy and complicated. But not impossible.

Huh...that really DOES simplify it all...I had initially wanted to do the "half of a round per round" thing because I wanted the submissions to be simple...but really Action/Bonus/Move isn't THAT much. And I especially like the idea that you could use reaction to change movement.

Thanks for the input!