Logopolis

This was the last "Dr. Who" episode for Who4, Tom Baker,
and the beginning for Peter Davison, the 5th 'Doctor'.
However the PREMISE was very interesting - some aliens
with extreme math abilities had constructed a math so
all-encompassing that it could create/change physical
reality just by being calculated.
In the plot the ultra-evil "Master" interfered with
the calculations - which were kinda supporting the
structure of the entire universe, bleeding off entropy
to a safe holding area, a custom alt mini-universe.
The most interesting bit though was the idea that
well-constructed math calx could actually affect
physical reality. SOME quantum stuff might kinda
suggest this to be true - 'observing' a system
affects that system - limiting exact calx/accuracy.
Properly crafted, such 'observations' could DRIVE
a system in a desired direction.
The first Who5 episode was kinda interesting in and
of itself, trapped in a very Escher-esque recurrent/
self-reflective little reality. "Where is your shop
on the map ? Well, it's right here ... and here ...
and here .......".
Anyway, these were all wonderful low-budget
masterpieces. Ideas/plot/dialog - those drove
it all, not computer-generated FX.
Oh, the saving bit for the universe ... "bubble
memory". Remember that ?  :-)