It has blocks in different arrangements- L shaped joined, three-in-a-line joined, single. Colours were red, blue and black. The objective of the game as I remember it was to put the tiles/ blocks together in different ways to make a pattern shown in a book that comes in the set, the over-all pattern usually contained in a square outline. Levels range from easy to hard, definitely a game that adults can attempt too. Someone said Tetris but it's nothing like that, although the blocks are similarly structured. Got this as a present when I was younger but I can't for the life of me remember what it's called.
It very much reminds me of a pentomino puzzle. Square board where you try to build certain shapes. I believe Tangram is a pentomino puzzle variant. Linked is an example of what I'm talking about (pieces are made of wood but you get the idea).
Good luck finding your game!
It looks similar to the Kaleidoscope Classic board game. One side is red and black, the other side is yellow, blue and black.