@sil The RNG seed only occupies 5 bytes from &D to &11 (13 to 17), location &12 (18) is the lower byte for TOP. But testing that code seems to cause a problems if more than the lower three bytes of the RNG seed are overwritten. Odd.

#bbcmicrobot 🚀
REM @sil
DIM M 1024
FOR L=13TO17:?L=?-444: NEXT
FORL=M TOM+1023 STEP4:!L=RND:N.
C%=1:A=0
REPEAT
O=FNround(C%)
T=A*C%
C%=-NOTC%
A=(T+O)/C%
PRINT"Pi after "; C%; " rounds is "; A*4
UNTILC%>10000
END
DEFFNround(X%)
F%=0:H%=0:T%=0
REPEAT
R%=((M?((X%/8)MOD1023))/2^(X%MOD8))AND1
IFR%=1H%=-NOTH%ELSET%=-NOTT%
F%=-NOTF%:X%=-NOTX%
UNTILH%>T%
P.
=H%/F%

had to work out a (very, very simple) maths thing about rolling averages (how do you keep updating the average of a set of numbers as new numbers come in, without keeping the whole list around), which I solved with baby's first algebra, so I wrote it down because I was quite pleased to have worked it out even though everyone will say "duh yeah that's obvious" 😊 https://www.kryogenix.org/days/2026/03/14/calculating-a-rolling-average-without-keeping-all-the-numbers-around/