brilliant
燦 centers on dazzling, radiant brilliance, like light sparkling or shining intensely.
燦 combines 火 (fire) with 粲, which likely contributes both sound and the idea of brightness or sparkling. The exact historical development of 粲 is uncertain, but the character as a whole expresses brilliant light.
Fire 火 on the left and 粲 (which looks like rice 米 under a roof with a hand 又) on the right: imagine a fire making rice sparkle brilliantly as it cooks.
For サン, picture the brilliant sun (サン) shining down on the fire: sun -> サン, and the whole scene glitters.