In Crystalline the player controls the character in an abstract universe. While collecting energy crystals the player must avoid the dangerous Chaos beings. Stopping them from dissolving the remaining crystal structures is the last hope of saving the crystalline beings.
Total conversion mods are cool and all, but have you ever been so bored that you said, out loud 'Oh my god, I'm bored.' That's what this experience is.
Very, very simple (to the point of being very short and slightly uneventful) yet still somewhat enjoyable, relaxing.