It may be tempting to use 240p as your target resolution if you are making a pixel art game since that was the resolution targeted by most retro systems and that many game developers are inspired by. If you are primarily targeting HD or 4K displays, consider instead choosing 180p as your target resolution, specifically 240x180 for 4:3 aspect ratio, and 320x180 for 16:9.
The reason for this is fairly simple, 180p offers a clean integer scale to all of the HD resolutions in common use today:
240p scales nicely to 720p (3x), 1440p (6x), and 4K (9x), but notably does not scale cleanly to 1080p, which is still seeing a considerable amount of use today.