button type="button" onclick="divide_scale();" style="width:32pt;">&frac12;</button>
		<input type="text" id="scale" value="4" onInput="draw_canvas()"/>
		<button type="button" onclick="multiply_scale();" style="width:32pt;">2&times;</button>
		</nobr>
	<br>
	<button type="button" onclick="snap_focus_to_nearest();">Snap to <i>f(x)</i></button>
	<button type="button" onclick="reset_focus();"><nobr>Reset focus</nobr></button>
	<button type="button" onclick="reset_scale();"><nobr>Reset scale</nobr></button>
	<