How to draw with the editor
Pick a canvas size first: 16 × 16 is the classic size for items and icons, 32 × 32 for characters, and 64 or more for portraits and scenes. Change it at any time with Resize, which keeps what you have drawn (anchored at the top left, or centred if you tick the box).
Draw with the left mouse button in the primary colour and with the right button in the secondary colour, which starts out transparent, so right-click erases. The fill tool floods one connected area of the same colour; the line and rectangle tools draw when you let go, and holding Shift keeps lines straight or at 45° and rectangles square. The eyedropper copies a colour from the canvas.
Turn on mirror mode to draw symmetrical sprites in half the time. Every action can be undone, and your current drawing is kept in this browser until you clear it.
When you are done, choose a scale and download the PNG. At 1× each pixel is one pixel, which is what game engines expect; larger scales are for sharing and printing, because every pixel becomes a crisp square block.