Kapla

KAPLA was was brought into the world in 1987 by Dutch antique-dealer and antiquary Tom van der Bruggen. He needed simple building blocks to help visualize his own Grand Designs project in S. France and Lego wouldn't do. Nor would any other commercially available product, so he invented and fabricated his own KAbouter PLAnkjes [en: gnome plankies]. It would have been my jam entirely, but even for The Boy [b. 1975] Kapla came a bit too late and we both had to make do with Lego. Each Kaplank has dimensions 11.7cm x 2.34cm x 0.78cm [ratio 5 : 3 : 1]. Using glue or Sugru, let alone nails, is considered cheating.

You can buy as many as you want can afford  here.
It occurred to me what the mark-up might be:

Best price is bulk price, buying 1,000 plankies at €240 is 24c each or 1c per cu.cm
You can buy an 8 ft length of 2 x 4 carpenter's timber: dimensions 240cm x 10cm x 4.4cm for about €6. That has enough to make 500 little planks . . . at about 1/20th the price. That's an option if you have a chop-saw, a sander and a lot of time . . . and don't forget PPE because saw-dust is carcinogenic.

Normal people hope for a rich and indulgent auntie to come through at Christmas.

 And the result is . . . building a huge 'dry-stone' tower and then causing its controlled demolition. So completely different from Jenga where the idea is controlled undemolition. Jengas are 7.5cm x 2.5cm x 1.5cm [ratio 5 : 5/3 : 1] and a standard N = 54 set can be had for €16-€20 from a toy store near you. The price for these slightly larger blocks is also about 1c per cu.cm. Pity the two systems are fabricated at different base dimensions.