There is a book about what you can do on the unexpanded ZX81
with only 1K of RAM, and really it isn't a lot.
There is also only about 1K of available RAM on the basic Ace,
once the operating system has taken its share, but this program
tape demonstrates better than any argument what you can do
with a 1K RAM when the language is Forth and not Basic.
Ten programs, a 14-page book for documentation and voice
recording on the tape to help locate each program, all for the
same price as many a single program has to be superb value,
especially when each application is also an object lesson in
economical programming.
Most of them are old favourites - Snakes, Gobbleman, Invade
and the like - which I would hesitate to claim as timeless
monuments to the human spirit.
But what really is great about them is the skill with which these
particular examples are written; you'll have no problem using VLIST
to study this.