Groove has 2 triggers to switch on the led, first in the led itself and second in the red flat button.
Size is great, fits comfortably in my hand, it doesn't use button battery, which is very good.
But here are my suggestions for next improvements
-Shorten the led click, so it is not interpreted as click-n-drag
-Soften the led switch, so only very small effort to click it, helps to preserve the led too
-Change the flat red button to other button with small effort button, touch sensitive, maybe
-Put a grip on it