Parser now treats ':' punctuations at the beginning of a line as a 'temp label' definition. Temp labels can be referenced by ':<num>' where <num> is the index number (zero-based) of the temp label.

src/assembler/parser.js

     return t;
   }
 
+  parseTempLabel(){
+    let isEOL = this.stream.eol();
+    this.stream.next();
+    if (isEOL){
+      this.__SKIPEOL = true;
+      return {
+        type:"temp-label",
+        val:-1, // Value of -1 means "set new temp label"
+        line:this.stream.line(),
+        col:this.stream.col()
+      };
+    }
+    let t = this.stream.next();
+    if (t.type === "number"){
+      t.type = "temp-label";
+      return t;
+    }
+    this.stream.die("Temp label missing index. New temp labels must be defined at the start of the line.");
+  }
+
   parseAtom(){
     if (this.isPunc("(")){
       this.stream.next();
         this.stream.next();
         return exp;
       }
+    } else if (this.isPunc(":")){
+      return this.parseTempLabel();
     } else if (this.isOpCode()){
       return this.parseOpCode();
     } else if (this.isDirective(".if")){
     }
 
     let tok = this.stream.next();
-    if (tok.type === "number" || tok.type === "string" || tok.type === "label"){
-      if (tok.type === "label")
-        return this.parseLabel(tok);
+    if (tok.type === "number" || tok.type === "string"){ 
       return tok;
+    } else if (tok.type === "label"){
+      return this.parseLabel(tok);
     }
     this.stream.die("Unexpected token {type:" + tok.type + ", val:'" + tok.val + "'}.");
   }