diff --git a/RP_L4/RPL4ENVIRON.cpp b/RP_L4/RPL4ENVIRON.cpp
index 4f122a9..2730510 100644
--- a/RP_L4/RPL4ENVIRON.cpp
+++ b/RP_L4/RPL4ENVIRON.cpp
@@ -267,6 +267,43 @@ namespace
 "# the old arrival-time behaviour if you want to compare.\n"
 "#RP412NETCLOCK=0\n"
 "\n"
+"# ---- Test harness -----------------------------------------------------------\n"
+"\n"
+"# The knobs that make a run repeatable and measurable. All are off\n"
+"# unless set and cost nothing when off; none belongs in a real race.\n"
+"# They exist so a claim about the game can be tested instead of argued.\n"
+"\n"
+"# Dump the gauge profile to rpl4.log every N seconds: every cockpit\n"
+"# display with its rate mask and tier, how often it ran and what it\n"
+"# cost. This is the engine's own ProfileReport, which was only ever\n"
+"# reachable from the arcade RIO mapper's F11 before.\n"
+"#RP412GAUGEPROFILE=8\n"
+"\n"
+"# 1 = log renderable construction and what each frame is made of, so a\n"
+"# model that never got built can be told from one that is simply out\n"
+"# of shot.\n"
+"#RP412RENDERDIAG=1\n"
+"\n"
+"# 1 = trace the player pod's position to rpl4.log on the SIMULATION's\n"
+"# own clock, stopping the pod dead at the green light so every run\n"
+"# starts from rest. Two runs of the same race then compare sample for\n"
+"# sample - this is the instrument that proved RP412PHYSICSHZ plays the\n"
+"# same race at every frame rate, bit for bit.\n"
+"#RP412PHYSTRACE=1\n"
+"\n"
+"# Try this drop zone first at spawn instead of a random pick. The pick\n"
+"# is seeded by RANDOM=, but a seed only repeats a run if the same\n"
+"# NUMBER of draws comes before the pick, and that count rides on load\n"
+"# timing - so pin the pad too, or two 'identical' runs start over\n"
+"# different ground. Falls back to the random walk if the zone is\n"
+"# taken, so it cannot wedge.\n"
+"#RP412SPAWNZONE=3\n"
+"\n"
+"# 1 = log the XInput-class controllers the generic-joystick scan skips\n"
+"# (attached DirectInput devices are always logged). For debugging a pad\n"
+"# that answers twice or a stick that does not answer at all.\n"
+"#RP412JOYLOG=1\n"
+"\n"
 "# ---- Optional ---------------------------------------------------------------\n"
 "\n"
 "# RGB keyboard lamp mirror (Windows Dynamic Lighting): keys bound to\n"