TITLE: GNOMON — the sundial garden
PROMPT: Create 'GNOMON', a garden sundial page: a serene Mediterranean courtyard with a stone sundial plinth; a gnomon shadow computed from the real local time and a draggable date ring (equinox to solstice), so the shadow's length and sweep are honest-ish astronomy; hour lines etched with roman numerals; hovering shows the equation-of-time note. Palette: travertine cream, cypress green, terracotta, shadow umber. Interactions: drag the sun along its arc (time scrubs, shadow follows with correct shortening at noon); a date ring shifts shadow angle across seasons; REAL TIME mode animates a day in 60 seconds with dawn/dusk regrading the scene; a small star chart appears at night. Ancient instrument, calm light.
DESCRIPTION: A Mediterranean courtyard rendered on canvas: travertine paving with joints, two cypress silhouettes, sky that regrades through dawn/day/dusk/night (stars and a moon after sundown), and a stone plinth with an elliptical dial plate etched with thirteen radiating hour lines and roman numerals. The gnomon casts an honest-ish shadow: its length follows 1/tan(solar altitude) with a season factor (short noon shadows at summer solstice, long winter ones) and its angle sweeps west→east across the day. Drag the sun slider to scrub 5:30–19:30, the season slider from winter to summer (with a note explaining each), REAL TIME to follow the clock, or RUN A DAY for a 60-second animation with full dawn/dusk regrades; a readout shows solar time and shadow length in gnomon-heights, plus an equation-of-time annotation.
TECHNIQUES: hour-angle solar geometry with season-scaled altitude and cotangent shadow length, elliptical hour-line projection on the dial plate, palette interpolation across six sky phases, canvas courtyard rendering (paving joints, cypress quadratic silhouettes, plinth with ellipse plate), night star field and moon, three time modes (manual/real/day) with slider sync.
INTERACTION: Drag the hour-angle slider to move the sun; drag the season slider to solstices; REAL TIME syncs to the clock; RUN A DAY animates a full day in a minute; readouts show solar time and shadow multiple.