sysconf topleft
global m[] nc .
gbackground 777
#
proc show .
   gclear
   scale = 100 / nc
   sz = scale * 0.95
   for i to len m[]
      x = (i - 1) mod nc
      y = (i - 1) div nc
      if m[i] = 0
         gcolor 000
      elif m[i] = 1
         gcolor 980
      elif m[i] = 2
         gcolor 338
      else
         gcolor 833
      .
      grect x * scale y * scale sz sz
   .
.
proc read .
   s$ = input
   nc = len s$ + 2
   for i to nc : m[] &= 0
   repeat
      m[] &= 0
      for c$ in strchars s$
         if c$ = "."
            m[] &= 1
         elif c$ = "H"
            m[] &= 2
         elif c$ = "t"
            m[] &= 3
         else
            m[] &= 0
         .
      .
      for i to nc - len s$ - 1 : m[] &= 0
      s$ = input
      until s$ = ""
   .
   for i to nc : m[] &= 0
.
read
#
len mn[] len m[]
#
proc update .
   for i to len m[]
      if m[i] = 2
         mn[i] = 3
      elif m[i] = 3
         mn[i] = 1
      elif m[i] = 1
         s = 0
         for dx = -1 to 1 : for dy = -1 to 1
            ix = i + dy * nc + dx
            s += if m[ix] = 2
         .
         if s = 2 or s = 1
            mn[i] = 2
         else
            mn[i] = 1
         .
      .
   .
   swap mn[] m[]
.
on timer
   update
   show
   timer 0.5
.
show
timer 0.5
#
input_data
tH.........
.   .
   ...
.   .
Ht.......