 counter
	this.i  = 0;        // index register
	this.dt = 0;        // delay timer
	this.st = 0;        // sound timer
	this.pitch   = 64;  // audio pitch register
	this.pattern = [];  // audio pattern buffer
	this.hires = false; // are we in SuperChip high res mode?
	this.flags = [];    // semi-persistent hp48 flag vars
	this.plane = 1;     // graphics plane
	this.profile_data = {};

	// control/debug state
	this.keys = {};       // track keys which are pressed
	this.waiting = false; // are we waiting for