Notion Dev (Notion Developer Platform) Japanese Edition Style Design System (DESIGN.md, Japanese UI)

Design policy: The entire page uses a "solid fill" background of cobalt blue #1313ba. A retro-blue base reminiscent of BSOD and mainframe terminals. The exact opposite of Notion proper (white-based) - Corners: Buttons and CTAs use border-radius: 0 (sharp squares). InlineTextLink etc. use 5px. Different from Notion proper's 8px - Density: The hero has generous whitespace; the data sync panel and code blocks are denser - Keywords: dev, BSOD blue, DOS, cobalt, sharp corner, dot-matrix, mono accent