Welsh roofing and writing slate has been split from the cliffs of North Wales since before 1900 — a riven blue-charcoal stone cleaved along its natural layers at Penrhyn and Cwt-y-Bugail. The face is cool, dark, and matte, its cleavage striations stacked like overlapping tiles on a Snowdonia roof.
This system distills that stone into an interface: a dark blue-grey ground, Payne's-grey and cool-stone supporting tones, and a single chalk-mark white — the scratched line of the slater and the schoolchild alike — as the only accent that lifts the dark.
威尔士屋面与书写板岩自 1900 年前便从北威尔士的崖壁中劈出——这是一种沿天然解理层裂开的冷调蓝炭灰石材，在彭林与 Cwt-y-Bugail 采石场被一层层剖分。石面冷峻、深沉而无光，解理纹理如斯诺登尼亚屋顶上层叠的瓦片般堆叠。
本设计系统将这块石头转化为界面语言：深蓝灰底色、佩恩灰与冷石灰的辅助色调，以及唯一一笔粉笔白——板岩工与学童在石面上划下的白色刻痕——作为唯一能在暗色底上提亮的点缀。整体保持哑光、剖裂、矩形层叠的质感，绝不出现奶白、纯白或任何暖色与高饱和色。