Feat: continue to improve documentation

docs/tutorials/variables.md

@@ -56,6 +56,10 @@ Reset on some condition:
 { 0 !n } @n 16 > ?    ;; reset after 16
 ```
 
+## When Changes Take Effect
+
+Within a single step, you can read back what you just wrote. But variable changes only become visible to other steps after the current step finishes executing. If step 0 writes `10 !x` and step 1 reads `@x`, step 1 sees the value from the previous iteration of step 0, not from the current one running in parallel.
+
 ## Naming Sounds
 
 Store a sound name in a variable, reuse it across steps: