commit 9f5eba09fa45e3e0a4cfddfc99f385c8c29e0738
Author: Leszek Koltunski <leszek@distorted.org>
Date:   Wed Aug 24 22:31:01 2016 +0100

    Correct an important bug in the vertex shader.
    
    b = 1/a if a!=0, 1 otherwise was incorrectly computed as b = 1.0 / (a+1.0-sign(a)). This, when 0<a<2^-24, suffers from 'round-off error': then a+1.0 = 1.0 (sic!) thus b = 1/0 !.
    
    Correct way: b = 1.0 / ( a - (sign(a)-1.0) )

diff --git a/build.gradle b/build.gradle
index 1d681fc..5aa08ec 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,7 +1,7 @@
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 22
+    compileSdkVersion 23
     buildToolsVersion "23.0.3"
 
     defaultConfig {