v1.4.0

Flux Hourglass 1.4.0

A small but very physical release. Rotate the phone and the sand and
LEDs now actually obey gravity, and the bottom controls finally stay
readable when they sit on top of a white pile.

Highlights

• Gravity-aware orientation. The accelerometer is sampled every
  frame and snapped to one of four 90° orientations (portrait,
  upside-down, landscape-left, landscape-right). The running screen
  rotates its content so the sand always falls from the physical
  12 o'clock toward the physical 6 o'clock, and the pile always lives
  on the gravity-down edge of the device. Hold the phone sideways and
  the sand falls sideways — the way you would expect.
• LED grid follows gravity too. The 16 × 32 LED grid fills from
  the physical bottom regardless of how you hold the device, matching
  the sand mode's behaviour.
• Readable PAUSE / RESET pills. The bottom controls now sit on a
  semi-transparent black rounded pill so they stay legible when the
  white sand pile (or a fully lit LED grid) reaches them. The label
  alpha also went up from 0.65 to 0.95 — they read clearly without
  having to stand out against the background alone.

Implementation notes

• A GravityOrient enum classifies device-frame gravity into the
  four 90° orientations with hysteresis: the dominant axis has to
  beat the other by 1.5× and exceed 5 m/s² before we snap, so a
  phone held near the diagonal does not flip-flop every frame.
• The running screen wraps its Canvas + overlay in a
  BoxWithConstraints that picks logical dimensions (swapped for
  landscape) and applies graphicsLayer(rotationZ = …) to the
  inner box. The physics never sees device coordinates — it always
  runs in a logical frame where +y is gravity-down. Tilt input
  is projected through GravityOrient.logicalGravity before being
  passed to ParticleSystem.update.
• ParticleSystem.initDimensions now rescales heights[]
  proportionally when the logical height changes, so an in-flight
  pile keeps the same fill ratio across a rotation instead of
  appearing empty or overflowing.
• Tap detection lives on the unrotated outer container, so taps
  resolve in device coordinates regardless of rotation while the
  visual content rotates underneath.