abstract appearance background black blended blue checked checks color colored colour coloured cool curved curves dark decorative design details glass glassy interconnected interlinked interwoven light lighting linear lined lines mosaic patterns perspectives plastic round rounded shape shaped shapes star style surface surfaces texture textured textures thick thin vibrant wallpaper board check Chequers chess chessboard contest diamond game play square strategy white wood wooden backdrop backing black-&-white chair decoration detailed fine horizontal intermeshed matt mesh modern nylon overlapping padded pattern stitched stitching strength strong vertical weave weaving woven accuracy antigen checking colloidal coronavirus covid-virus detection diagnosis diagnostic-aid dropper drops extraction-reagent-tube home-use immunochromatographic-technology kit limitations limited lysis-buffer measuring-instrument medical nasal nasal-secretion quality-control-C-line rapid rectangular sample sampling-tube self-testing sterile-swab swab test test-cassette testing check up cleaning crown dental dentist Doctor drill health hygiene oral pick smile teeth tools diagram ecg electrocardiography healthy heart hospital medicine results vital break broken checker checkerboard checkmate close king knight oak sharp win