Java 12 and stelo.Spread
It seems that stelo.Spread/stelo.PastFuture etc. is compiled with Java version 56 (Java 12), so it cannot run on Java 8 roborumble clients which was a de facto standard.
Shall we upgrade all clients to Java 11 and release new robots with Java 11, or remove all robots compiled with Java 9+?
Anyway Java 12 should never be supported as it's not LTS.
Worth mention that Java 9+ is not fully backward compatible with robots compiled with Java 8, etc. ByteBuffer related functions has ABI changes in JVM, so it breaks.