Cube / HTML validation
The interactive viewer is not validated by appearance alone. The suite builds a cube from real PRISM maximum temperature, extracts the six base64 PNG textures from the generated HTML, decodes their RGBA pixels, and compares every pixel to an independently indexed source array.
Declared face contract
The front of the cube is the newest date and the back is the oldest. CSS rotates opposite faces in opposite directions, so source arrays are oriented before encoding:
| Face | Source evidence | Declared display direction |
|---|---|---|
| Front | newest time × y × x plane |
x unchanged |
| Back | oldest plane | x reversed for rotateY(180deg) |
| Left | x-min boundary through time | oldest at back, newest at front |
| Right | x-max boundary through time | time reversed before rotateY(90deg) |
| Top | y-min boundary through time | oldest at back, newest at front |
| Bottom | y-max boundary through time | time reversed before rotateX(-90deg) |
The renderer now uses background-size: 100% 100% for cube and interior
textures. The previous cover rule cropped rectangular space-time textures to
a square and could hide evidence on the side faces.
Acceptance requires exactly one of each shell face, no cropping CSS, the stated orientation for all axes, and exact equality for every decoded RGBA pixel.