Note that we wait for a space character (32) or either kind of new-line which typical ASCII keyboards produce (10 or 13), just to be on the safe side:

[ TitlePage i;
   @erase_window -1; print "^^^^^^^^^^^^^";
   i = 0->33; if (i==0) i=80; i=(i-50)/2;
   style bold; font off; spaces(i);
   print "                     RUINS^";
   style roman; print "^^"; spaces(i);
   print "         [Please press SPACE to begin.]^";
   font on;
   box "And make your chronicle as rich with praise"
       "As is the ooze and bottom of the sea"
       "With sunken wreck and sumless treasures."
       ""
       "-- William Shakespeare, ~Henry V~ I. ii. 163";
   do { @read_char 1 0 0 i; } until (i==32 or 10 or 13);
   @erase_window -1;
];