While playing the game, press Start to display the options menu. Although the touch screen is obscured, the timer will stop. You can then look at the top screen and take as much time as desired to determine your next move. Resume the game, make your move, then pause the game again and repeat.
Accumulate 20 stars by ranking well after solving puzzles to unlock 50 puzzles.
Accumulate 40 stars by ranking well after solving puzzles to unlock 70 puzzles.
Each level has a different number of stars you can get. "Practice" and "Easy" give you a maximum of four stars. "Normal" gives you a maximum of five stars. "Hard" has a maximum of six stars. After collecting twenty stars, new levels will open up (usually thirty new puzzles for every twenty stars).