Kotlin and Android Development: Could not get unknown property ‘kotlin_version’…

Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in python, js, and - in a basic, command line form - in kotlin and want to port it to Android (web version at https://basilisk.net). Anyway, got to page 8 and was editting the build.graddle file and found that the line

implementation “org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version”

threw up an error “Could not get unknown property ‘kotlin_version’…”

the line jvmTarget = ‘1.8’ was already in the build.graddle file but the dependencies identified were not. Editting out the problematic kotlin_version line and the program runs fine, but I don’t want to waste my time if this is something that causes more problems downstream.

I am on Arctic Fox 2020.3.1 Patch 1.