'
' Dr. Necro
' By Ken Schafer
'
' Revision History
' ----------------
'
' Ver 0.62     8/6/92
' -------------------
' New concept for virus animations.  Viruses are animated round robin style, a
'  few each interrupt.  This should spread the load more evenly, and perhaps
'  increase performance to an acceptable level.
'
' Ver 0.61a    2/8/92
' -------------------
' Re-vamped sprite system, routines for virus animation added
'  animation is too much of a drain on processor resources.
'  barely playable on a 16MHz machine.
'
' Ver 0.60 -- 12/14/91
' --------------------
'  Internal Cleanup in preparation for C translation
'     (check_lines and erase_lines are MUCH nicer)
'
' Ver 0.58 -- 11/20/91
' --------------------
'  Fixed small bug that occasionally preventing game from ending
'     when it should (Stooooooopid mistake!)   (thanx Mom!)
'
' Ver 0.57 -- 7/31/91 -- RELEASED AS VER 0.85b (oops!)
' -------------------
'  Joystick routines added(0.57)
'  Sadistic music added as an experiment(0.56)
'
' Ver 0.55 -- 6/23/91
' -------------------
'  Levels now function. Game is playable as is
'  Needs Title Screen, sound, animation and cleanup
'
' Ver 0.52 -- 6/21/91
' -------------------
'  Added routines to implement virus display and scoring
'
' Ver 0.50 -- 6/21/91
' -------------------
'  Lots of Changes -- Pills now have proper shape (tops, sides etc)
'  Added all changes to checking routines to implement various shapes
'  Pills that are linked now have bonds and hold each other up!
'
' Ver 0.40 -- 6/19/91
' -------------------
'  Replaced boxes with actual bitmaps
'  Added Background Picture --------- Things are getting REAL cool!
'
' Ver 0.31 -- 5/26/91
' -------------------
'  Added routines to allow individual pill pieces to fall
'
' Ver 0.30 -- 4/20/91
' -------------------
'  Added boxes instead of debug numbers
'  Began Coding routines to check/erase lines
'
' Ver 0.21 -- 4/18/91
' -------------------
'  First version as Dr. Necro
'  Replaced screen point checking with an array lookup -- much faster
'
' Ver 0.14 -- 1/20/91
' -------------------
'  Originally the beginnings of a Tetris clone...
'  The main logic for Dr. Necro was "extracted" from here.
'