Instead of reaching for some awful costume-in-a-bag because you put off deciding what to be this Halloween, quickly transform your look by creating this painted on bat-shaped, glittery mask. Follow these step-by-step instructions courtesy of Genoa Norris, Resident Trainer at MAC Cosmetics and you'll have a costume in no time. Pair this mask with all black clothes and a sleek ponytail for a complete (and super simple!) look.

Map out the shape you want to create around your eyes by using a nude lip pencil (try Wet n Wild Cr�me Lip Liner in Brandy Wine, $.99). Drawing the shape in nude pencil makes it easier to fix mistakes until you have the ideal shape for your mask. We chose a bat-like shape.

Once your mask shape is set, start filling it in with black cream makeup (try MAC Paint Stick in Black Black, $19, available only at MAC Pro stores) using a flat, stiff makeup brush. You'll want to fill in every area of the mask, which includes painting over your brows with the cream.

Using the same brush, press teal-colored glitter (try MAC Glitter in Reflects Turquatic, $16.50, available only at MAC Pro Stores) onto your eyelids and along your lower lash lines.

Continue with glitter, but this time switch to using a whitish-gold glitter (try MAC Glitter in Reflects Gold, $16.50, available only at MAC Pro Stores). Press the glitter into the black cream makeup wherever you didn't apply the teal glitter. To clean up glitter that may have landed outside the mask lines, use a piece of Scotch tape to pick it off your face. Finish the look with a neutral-colored lip gloss.