/* meteor.tc

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

/* implemented lrb - 12/3/7

/* added chide, cnormal - 12/6,9/7
/* changed screen dimensions to 50x80 - removed several functions
/* which are now in the system library - 5/17/9

int speed

star [
  speed=2000;cls
  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
  /* fill screen with fixed stars
  while (++k<stars) [
    plot random(1,50),random(1,80),1
    pause speed
  ]
  k=0
  /* launch colored shooting stars
  while (++k<shoots) [
    color random('1','7');shoot
  ]
  color '7';cls;cnormal
]

/* fire a shooting star

shoot [
  int k,start,big,delta
  start=random 20,60
  big=random(1,2)*random(1,2) /* 1 or 4
  delta=random -3,3
  while (1) [
    ++k;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=50;C=80
  if ((r>=1)*(r<=R)*(c>=1)*(c<=C)==0) return 1
  MC 27,1 /* ESC
  MC 91,1 /* left bracket
  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
]

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