It's time for some game logic! From the very first outline of this project, I wanted to have an engine that used an interpreted scripted narrative to run the game. It is time to start work on that.

The last piece of the puzzle was to implement a global game state. This does a couple of things, but the most important thing is, it stores changed values per scene per object and when a scene (re)-loads, those values are put back. This means if you pick up an item in one scene, go to the next and then return, the item will still be picked up. Having a global game state also makes it easier to implement saved games and do quick testing of various game scenarios.

But now I want something to do in the game. I have not yet made the inventory system, but that is a bolt on accessory that I do not need for this. What I want is for each scene to have a storyboard with an easily readable script that is able to define actions and subsequent reactions all with some logic thrown in there. For this I took some inspiration from other game scripting languages and general scripting languages.

I want the least amount of syntax and maximum readability. That is why I chose to use an indent type of logic that interprets something that kinda resembles the verb based system SCUMM used, but not quite! Here is a snippet.

<storyboard>

    use stick on bolder
        case bolder.pushCounter = 3
        say "enough already!"
        break
    esac
    set bolder.pushCounter ++
    move bolder add 10 0
    play grind
    say "Uuurrggg...."
    case bolder.pushCounter = 3
        say "Well, that went better than expected!"
        hide bolder
        break    
    esac
    use bag1 on bolder
        say "That does not seem to work."
    break
                        
    lookAt bag1
        say "That's my bag!"
    break

    lookAt stick
        say "It's a stick! Made of wood."
    break
                                        
</storyboard>

The main part here of course is the "use stick on bolder" line. In this case, it is not a description of what can be done, but a label of what to do when this happens. The game engine itself will generate that set of words and will then search the script for this occurance. If it is there, the script level goes up and interprets every line on that level until it breaks or the level goes down again.

Specialized function like say, hide and play are abstracted versions of their actual engine counterparts. It is still possible to directly change game state via the set command. In fact, most commands could be done with set, only it would take more commands to do the same thing like move that would need several in this case as it not only sets an object x and y position, it adds to it which means that you'd need to use set about 6 times making the script less readable.

Another example would be the hide command which does 2 things. First obviously it hides the object but more importantly it sets the global. The alternative version isn't much longer, but it is longer none the less.

case bolder.pushCounter = 3
        set bolder.hidden true
        global bolder.hidden
        break
esac    

For commands like say, it would be even more involved as it would mean setting various object attributes and figuring out what object to do it to. The say functions just does that for me.

At this moment, the script does indeed run and most functions are implemented. There are a few things I need to clean up and test, but I think this is looking very promising.