Yal's Monster Collector Engine

Here's the official GameMaker tutorial series on the code editor. (I recommend using GML Code since Visual doesn't really make things easier, just prettier to look at.)

The part which applies the move is the part (starting at line 671) which begins:

//Apply to all target(s) individually
for(var c = 0; c < array_length(a_targ); c++){

Currently it doesn't do anything special to detect targets not existing, it checks if the number of hits is 0 and the number of misses is also 0 to conclude that there was no target after the fact. (Done immediately after this loop)

So what I'd do is insert a check before this loop, which checks if the original target remains, otherwise gets a random one based on the move (using the function enemies use to pick random targets):

found_targets = 0;
for(var c = 0; c < array_length(a_targ); c++){
     var trg = a_targ[c];
     if(battle_is_alive(trg)){
         found_targets++
     } 
}
if(found_targets == 0){
     a_targ = battle_get_random_targets(a_user, a_comm); 
}

I tried it out and also can see it, so something has changed with GM's processing order that causes this (it was always a bug but it just didn't happen before for some reason, lol - presumably the player was always handled before the dialogue boxes but now it's handled after and thus retriggers the interaction immediately after it closes)

It's easy to fix at least, just update the "Interacting" block of obj_player's step event like so:

//Interacting
if(interaction_cooldown){
     interaction_cooldown--
}
else{
     if(k_a && !p_a){
         var o = collision_circle(
             x + lengthdir_x(TILESIZE,drawdir) - TILESIZE*0.5,
             y + lengthdir_y(TILESIZE,drawdir),
             12,
             parent_interactible,false,true
         )
         if(o > 0 && instance_exists(o)){
             interaction_cooldown = 5
             with(o){
                 if(object_index == obj_npc || object_is_ancestor(object_index,obj_npc)){
                     drawdir = (other.drawdir + 180) mod 360
                 }
                 if(interact_script != NONE){
                     script_execute(interact_script)
                 }
             }
         }
     }
}

Then just initialize interaction_cooldown to 0 in the Create event and everything should work as expected.

Yeah, all of the grid stuff will need to be custom-made, because there's no concept of positioning and ranges in the engine currently.

What I'm thinking will need to change:

• obj_battlemonster currently just has its position as a visual thing, it will need to be able to move around... but more importantly they need to keep track of their current grid cell (because that's ultimately what matters, their x/y position is just a representation of that)
  • obj_battlemonstercircle is just a visual object representing the ground currently, but could probably be repurposed into grid squares; you'd give them variables for which grid cell x/y they represent and then be able to use them for reference for where to place monsters + maybe let them keep track of which cells are occupied or not. And then rather than always creating two, you'd create enough for the entire grid.
• battle_get_valid_targets needs to take positioning and range into account, and in turn move data needs some new stats to store those (which would be added to init_moves/init_move).
  • Additionally, mev_battle_attack and bcontrolstate_ACTIONSELECT_ENEMY should be updated to do nothing if there's no valid moves to use instead of enqueueing the desperation attack (unless there's a target in range)
    • bcontrolstate_ACTIONSELECT_ENEMY additionally will need to select a new "move" action sometimes, e.g. when there's no targets in range. (And presumably you'll need to add a new action to the player action selection menu as well for moving, see bcontrolstate_ACTIONSELECT_PLAYER)
  • mev_battle_attack_select currently creates a menu to select targets when there's multiple targets and a move targets a single target; you could keep this menu but have it also discriminate by range and positioning. If you're OK with it just listing targets that should essentially be the only thing you need to do, but if you want it to highlight the grid cell you're targetting it gets a bit more involved - creating a GGUI region with no background sprite which covers the entire grid, then placing highlight regions so that they line up with individual grid cells. (Check out msh_terminal_load_page's section "Middle main: Box contents" for an example of how to make a grid menu, but the TLDR is that you want one "ggui_menu_region" for each cell, after ggui_menu_preallocate'ing a grid with as many cells as your battle grid). These cells's menu event field would be filled in with NONE if there's no valid target there, mev_battle_attack_select_target if there is.
  • Likewise, you'd do basically the same thing for selecting a cell to move to, except you have NONE if a cell is occupied and a new mev_battle_move_confirm_destination event if it's not + within your move range. (You'd probably want to add sprite elements to each cell which are just a red/green rectangle which represents if it's valid or not)
• Currently obj_battlemonster remains even if the monster is KO'd and just is invisible, you'd probably want some extra logic to move them out of the grid when they're not replaced with backup so that a dead monster can't impede pathfinding and be selected as a valid target. Just setting their grid cells to a big negative number (like NONE) might be enough, as long as you don't try actually accessing the grid data if the position is NONE.

The change was to not modify argument0 directly, but to use a helper variable to hold it (I don't remember what the compilation error was but presumably argument is read-only after 2.3)

The current version looks like this:

///tsprintf(format,...)
function tsprintf() {
     //Trivial String Print Format
     //Replaces each % percent sign with an argument, then returns the string.
     //Inteded to make writing debug printouts less painful.
     var c, s = argument[0];
     for(c = 1;c < argument_count;c++){
         s = string_replace(s,"%",string(argument[c]));
     }
     return s;
}