Chaos checks

In september last year, I wrote about ‘Vinken’ or ‘Checks’, a Sanders puzzles publication. My main comment was that it was a nice puzzle variation, but that the puzzles were slightly too easy. Sanders puzzels corrected this in later issues.

I did come up wit a slight variation, though the puzzle I designed didn’t make the puzzle difficult enough for my tast. Anyway, I’d like to present this variation to the world.

The rules are simple:
– every row and column, and every 9 sized area, contains 3 checks.
– the checkmarks are never adjacent horizontally or vertically. They may be adjacent diagonally.
– some checkmarks have been pre-filled, as well as some empty squares.

Here are three examples.
puzzle 1^*
As you can see some checks and some empty positions have been given. You hve to derive the position of the remaining checks.

puzzle 2^*
This time only some empty positions have been given as clues.

puzzle 3^**
Again only some empty positions have been given as clues.

You can check your solutions here

A new puzzle is published every Friday.

1000

A prime number is a number that can only be divided by 1 and by itzelf. Examples are 2, 3, 5, 7, 11, 13 and so on. You can find the first 1000 prime numbers here.

Now here is a quicky: write 1000 as the sum of as many different primes as possible.

You can check your solutions here

A new puzzle is posted every friday. You are welcome to comment on the puzzles. Solutions are added at the bottom of a puzzle after one or more weeks.

Remove 4 matches so that you have 5 squares left

This puzzle can be found over and over again in books with matchstick puzzles. Sometimes just one solution is given, though often two solutions are presented. In fact, there are at least 8 different solutions.
Those eight are AFTER discarding rotations and mirror images.
Can you find them all?

You can check your solution here

The two squares (2)

What code corresponds with the figure in the centre?

You can check your solutions here