I love almost everything about this and dislike only a few things:

As k__ pointed I see no point in including semicolons, if you already have parenthesis that can be used to delimit expressions and newline characters, why include ";" ?

Another thing that I don't like is how the language is encourages type weakness in circumstances that normally lead to a dozen pointless bugs in my software during the development process:

    a = -1

    if a { // Actually meant a > 0
      console.log("In if");
    }

This could be avoided if languages didn't implicitly convert int, float etc values into boolean in the conditional expression of if. The result wouldn't even need a lot more code

    if Boolean(a) {

That would probably require more code to implement into Spider in sections that might be performance critical. CG coders love to use those binary shortcuts in their code.