diff --git a/apps/build.gradle b/apps/build.gradle
index 67664e9..40bc44d 100644
--- a/apps/build.gradle
+++ b/apps/build.gradle
@@ -17,9 +17,9 @@ if (!hasProperty('mainClass')) {
 jar.manifest.attributes('Main-Class': application.mainClass)
 
 ext {
-    // which BTF (buildType + flavor) of the native physics library to use:
-    //btf = 'DebugSp'
+    // which BTF (buildType + flavor) of the native physics library to download:
     btf = 'ReleaseSp'
+    //btf = 'DebugSp'
 
     fs = System.getProperty('file.separator')
     downloadsDir = System.getProperty('user.home') + fs + 'Downloads' + fs
diff --git a/common.gradle b/common.gradle
index 1cfa22a..35f4961 100644
--- a/common.gradle
+++ b/common.gradle
@@ -1,7 +1,7 @@
 // Gradle settings and tasks common to all V-Sport subprojects
 
-apply plugin: 'checkstyle'
-apply plugin: 'java'
+apply plugin: 'checkstyle' // to analyze Java sourcecode for style violations
+apply plugin: 'java'       // to compile and test Java projects
 
 java {
     sourceCompatibility = JavaVersion.VERSION_1_8
diff --git a/lib/build.gradle b/lib/build.gradle
index 9faa446..8411542 100644
--- a/lib/build.gradle
+++ b/lib/build.gradle
@@ -5,9 +5,9 @@
 //   of the root project.
 
 plugins {
-    id 'java-library'
-    id 'maven-publish'
-    id 'signing'
+    id 'java-library'  // to build JVM libraries
+    id 'maven-publish' // to publish artifacts to Maven repositories
+    id 'signing'       // to sign artifacts for publication
 }
 
 ext {