I watched the video. Very interesting, well done

It's no replacement but it is huge fun once you learn it, which isn't hard. You can get to a point where you are rolling off ideas like you are dictating directly to the computer. Here's the meat of the pink bouncing ball's script:

: >bounce  sin abs negate 24 * ;
: draw-bouncer  draw> zofs 65 tile ;
bouncer :to start
    draw-bouncer 0 perform>
        begin 3 + dup >bounce z !  pause again ;

Factor out a couple theoretical utility words and you could do the same thing with even less effort:

bouncer :to start  65 draw-ztile  0 perform> 3 24 sinbounce ;

The possibilities are almost intoxicating. No types, no headers, no compile time (it's instantaneous). It's a limited space, but it has strengths.

It's simple just read it left to right. Parameters go first, i.e. it's postfix so you don't 1 + 2 you 1 2 +. : and ; start and end a function definition and apart from flow control (if/then) and understanding the VM and dictionary that's pretty much it.

Because it compiles fast, and actually it's easier, there's never any ambiguity about order of operation and it's easier to factor.

I actually think the version you wrote out is a headache! Understanding the transformations numbers go through step-by-step is effortless in postfix.

A game engine to make games with FORTH? Nice!!!

I actually never used FORTH but I made a scripting language inspired by it, even used it in a game engine mock-up to build interactive fiction games. It was pretty easy to use, actually.