/* meteor.tc

/* Meteor shower program, by T. A. Gibson, Nov. 1977.
/* Demonstrates use of random and plot.

/* implemented lrb - 12/3/2007

/* added chide, cnormal - 12/6,9/2007

int speed

/* main program

star [
  speed=2000 /* set speed
  cls /* clear screen
  pl"Please enter a random number between 0 and 100 ";seed=last=gn
  int k,stars,shoots
  ps"How many fixed stars do your want? ";stars=gn
  ps"How many shooting stars do you want? ";shoots=gn
  cls
  chide /* hide text cursor
  /* fill screen with fixed stars
  while ((k=k+1)<stars) [
    plot random(1,24),random(1,80),1
    pause speed
  ]
  k=0
  /* launch colored shooting stars
  while ((k=k+1)<shoots) [
    color random('1','7');shoot
  ]
  color '7' /* reset back to white
  cls
  cnormal /* normal text cursor
]

/* fire a shooting star

shoot [
  int k,start
  start=random 20,60
  int big
  big=random(1,2)*random(1,2) /* 1 or 4
  int delta
  delta=random -3,3
  while(1) [
    k=k+1
    pause speed
    plot k,start+delta*k,1 /* plot head
    /* erase tail - leave when at edge
    if (plot k-big,start+delta*(k-big),0) if (k>big) break
    /* large shooting stars, aka cruisers, erase nearby fixed stars 
    if (big>3) [
      plot k-big,start+1+delta*(k-big),0
      pause speed
      plot k-big,start-1+delta*(k-big),0
      pause speed
    ]
  ]
]

/* positions cursor at row r, col c if on screen and returns 0 
/* just returns 1 if off screen

int R,C

plot int r,c,onoff [
  R=24;C=80
  if ((r>=1)*(r<=R)*(c>=1)*(c<=C)==0) return 1
  MC '\'-1-'@',1 /* left bracket = backslash - 1
  MC '\'-1,1
  pos r;MC ';',1;pos c
  MC 'H',1
  if (onoff) MC '*',1;else MC ' ',1
  return 0
]

/* helper function for plot

pos int rc [
  if (rc>9) [
    MC rc/10+48,1;rc=rc%10
    ]
  MC rc+48,1
]

/* clear screen

cls [
  MC '\'-1-'@',1
  MC '\'-1,1
  MC '2',1
  MC 'J',1
]

/* pause k units

pause int k [
  int l;while ((l=l+1)<k) []
]

/* 0=black 1=red     2=green 3=yellow
/* 4=blue  5=magenta 6=cyan  7=white

/* set foreground color

color char c [
  MC '\'-1-'@',1
  MC '\'-1,1
  MC '3',1
  MC c,1
  MC 'm',1
]

/* return random integer between low and high, inclusive

int last, seed
random int low, high [
   int range
   if (last == 0) last=seed=99
   range = high - low + 1
   last = last * seed
   if (last < 0) last = -last
   return low + (last/7)%range
   ]