Force and extension
F = k × e
Spring:
Rate
Steady
Accessibility — Adapt
Theme
Dark navy theme
Colour overlay (Irlen)
Off
Display
Reading ruler
Wider spacing (dyslexia)
Text size
100%
High contrast
Classroom / projector mode
Show extension markerA shape-coded arrow on the ruler, not just colour.
Procedure
No dragging — buttons onlyEvery drag becomes one button press. Perfect technique assumed.
Motion
Reduce motion
Slow animation
Auto-rotate camera
Colour vision
Protanopia
Deuteranopia