Use grenades to clear a path around the perimeter.

Actually, scratch that.  In excessive, you need to grab the flamethrower, stand in the center, and madly spin around in circles while throwing grenades.  That should buy you about 35 seconds right there.  Hey, I beat Greg’s score of 11,000,000 by about 785,000 points!  All hail the new champ!  (lol . . . that’s so sad) 

Highscore setting becomes an issue of how much patience you have running around in circles with mines.

Yes . . . that’s why I said that it’s “so sad!”  The person with the highest score is usually the person without anything interesting to do.