Here is the full list of all 8 Pixross achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Complete 150 puzzles
Complete 100 puzzles
Complete a 15×15 puzzle
Collect 10 style options
Complete a puzzle using the bomb challenge
Collect 1,000 stars
Complete a 10×10 puzzle
Complete a 5×5 puzzle