"LIXSO = I,X,S & O in an L "

Lixso is a new and original logic game, somewhere in between Sudoku and a puzzle. Fill a grid entirely using L-shapes with the 4 colors (or matching symbols I,X,S & O), respecting the pre-filled cells, and in such a way that L-shapes with the same symbol/color don’t touch – neither on a side or a corner.
Read more detailed rules here
​It sounds easy, but there are many ways to fill a 9 by 9 grid with L-shapes.  Each grid has only a single correct solution, you will need to use logical reasoning to find it. There are 6 difficulty levels. Try level 1 or 2 to learn the game – one can easily see which symbols fit or not, and with each added L, others become clear. But for level 4, 5 or 6, it is more difficult. Sometimes you have to imagine or place a whole chain of L-shapes to find out if it leads to the solution. First, place those L-shapes of which you are certain. Do observe the entire grid, as sometimes you have to continue on a whole other part of the grid.