I am making a little turn based strategy game in pygame, that uses a grid system as the main map to hold all the characters and the map layout. (Similar to Fire Emblem, or Advance Wars) I am trying to determine a way to quickly and efficiently (i.e. without too much of a slow down) check if there are any characters within a given range of the currently selected character. So to illustrate: O = currently selected character X = squares within range Range of 1: X X O X X Range of 2: X X X X X X O X X X X X X Range of 3: X X X X X X X X X X X X O X X X X X X X X X X X X Now I have to tell the user who is in range, and I have to let the user choose who to attack if there are multiple enemies in range. If I have a 5x5 grid, filled with " " for empty and numbers for the characters: [ ][ ][ ][ ][4] [ ][1][ ][ ][ ] [ ][ ][ ][ ][ ] [ ][ ][2][3][ ] [ ][ ][ ][ ][ ] Depending on which character the user selects, I would like to show the user which other characters are in range. So if they all had a range of 3: 1 can hit 2 2 can hit 1 or 3 3 can hit 2 4 cannot hit anyone. So, How do I quickly and/or efficiently run though my grid and tell the user where the enemies are? PS- As a bonus, if someone could give an answer that could also work for a minimum distance type range, I would give them a pat on the back and a high five, should they ever travel to Canada and we ever meet in life. For example: Range of 3 to 5: (- is out of range) X X X X X X X X X X X X - X X X X X X - - - X X X X X X - - O - - X X X X X X - - - X X X X X X - X X X X X X X X X X X X