I am trying to make the sprite respond to a stimuli while performing something. But it seems that creating a infinite loop with an if/else statement does not make the sprite very responsive. My normal activity has a execution time span so reducing the time span makes the activity seems unnatural, but increasing it reduces the responsiveness. Can I have a suggestion for a better script?

when green flag,
forever,
if stimuli happens, perform special response etc

else normal activity

Put everything inside the Forever loop into a CUSTOM BLOCK. For that block, set the RUN WITHOUT SCREEN REFRESH option.

Disclaimer - without seeing what is in the loop, that may be terrible advice.