VALUE Toast gradient. Human eyes can perceive 255 distinct levels of values (shading). If someone can find toast with 15 different levels, surely you can have more than just 3 or 4 in your drawings and paintings.
Do you have old light bulbs that are not broken? Instead of just throwing them away, you can repurpose them as some creative things. Check out this list of Creative Light Bulb DIY Ideas and try one of them.