100 Cross-sums Puzzles

This book contains 100 Cros Sums created by LOGI, the leading Polish puzzle publisher.
Inside you will find 100 puzzles different sizes, from 9x13 till 18x26, different difficulty levels.
How to solve? Into white fields insert numbers from 1 to 9. White numbers in black fields are the sums of the inserted numbers (e.g. 23 = 9 + 6 + 8). The numbers cannot repeat within one sum.
Solve free cross sums at http: //www.wydawnictwologi.pl/krzyzowki-logiczne
Reasons to like Logi puzzles:

1. Each puzzle has only one solution.
   Puzzles are tested by a computer program designed by Urszula Marciniak, a mathematician and puzzle lover.
2. You can solve puzzles using only logical thinking - no guessing is needed.
   The program is designed so that it uses only human kind of thinking. So even if a puzzle has only one solution, the program can reject it, because human will not be able to solve such puzzle without guessing and finding contradictions. This is what makes Logi puzzles enjoyable to solve.
3. Puzzles are created by professional graphic designers.
   We have very high standards for graphics. We don't accept all images, they have to fulfill certain conditions, like no empty lines, clarity, and many other.
4. We set five difficulty levels.
   The levels are set by a computer program, so they are always objective and the same.
5. No repeating puzzles.
   The puzzles you see in this book are not published in any other non Polish language book. They were only published in our Polish monthly magazines available in Polish press stores or in online store at our website.
6. We publish puzzles since 2004 - we know well what puzzlers like.
7. If you have problems with solving a puzzle send it to us and we will show you a next step.
   Although puzzlers prefer to solve puzzle alone to feel proud, sometimes a small tip can be very helpful. We provide such help all the time for Polish puzzlers.
8. If you are new in puzzles you can check our website for tutorials www.logi-puzzles.com.
   Go to the Friday Online Mix section and click below a specific puzzle to see tips and tricks.

The person who takes care of Logi's high quality is Urszula Marciniak - the founder of Logi.
Mathematician, photographer, a puzzle fan