2.5 Visuals

V keeps Swarm Synth IV's simple, retro visual language — thin glyphs, small monospace text, a red accent, three sliders — but its main theme is white: black boids and text on white paper. IV's dark look remains as the theme night; the other themes let the sounds colour the stage (below).

Boids (b cycles): 1 arrow (the start), 2 triangle, 3 line (10 px at Full HD), 4 oval (4 × 6 px, solid in the theme's ink like the other glyphs; IV's was a faint 6 × 9). Lines and arrows are drawn at alpha 230 and never thinner than 1 px on screen (thinner lines blurred away on a laptop); triangles and ovals at 200.
IV's three sliders (separation, alignment, cohesion): the middle one at the centre of the stage, the others two 120 px grid cells above and below — Full HD 300, 540, 780 (IV: 270, 540, 810). The beat grid is centred too, so all three lie on grid lines at every grid step (40, 60, 80, 120, 240). Each is a band with a thin upright marker at the current value (5 × 20 px at Full HD; IV's was a square); the slider being played lights up. At rest the band is alpha 18 and the marker 75, so the current values stay readable; while a value is changing — by mouse, keys or a score — its band and marker rise to 36 and 150 and fade back in about half a second. The labels are solid white; “> ” marks the one the arrow keys play, as in the HUD.
Geometry overlay (g, on at the start): each flock's centre, mean heading (length = polarization), spread ellipse and size. Flocks with a voice are drawn in red, forming or unvoiced flocks in grey. Small red rings mark where encounter notes sound, after IV's trigger circles.
HUD (h): max speed, max force and status top-left; measures top-right under the credit “Swarm Synth V / © Bumi Ko”. Text is 14 px at Full HD and never smaller than 12 px, solid white (the selected parameter is marked with “> ”), set in Source Code Pro (monospace, SIL Open Font License).
Background: plain white in the main theme (paper), plain black in night (IV's look); the coloured themes below let the sounds colour it, as IV tinted its black with its trigger notes and sine strings.

Themes (keys 1 – 3; in a score theme night etc.). cmy and vivid are set aside for now: no key, but a score can still name them. Only the picture changes; the sound never depends on the theme. Scores name their themes, so reordering the keys never changes a score. The main theme is the one on key 1 (paper): free play starts in it, and so does a score without a theme line; returning to free play keeps the theme being played. Shift+R takes always name their theme.

key	theme	background	ink and flocks
1	paper	the inverse of night: plain white	black; voiced flocks red; inside each flock's ellipse a faint wash of its voice colour, strongest at the centre and fading to the edge, behind the boids, as in vivid (hue = pitch, saturation = order): a scattered flock barely tints the paper, an aligned one clearly (key `c`)
2	wash	the same three layers as cmy (magenta notes, cyan beats, yellow drones forming or swelling) mixed into one colour for the whole stage, gliding to each new mix in about a quarter of a second; silence is white	black
3	night	plain black — IV's look	white; voiced flocks red
4	cmy	a vertical map of the sound: magenta (notes), cyan (beats) and yellow (drones forming or swelling), each painted at the height where it sounds — height is pitch — and fading within about 1.5 s; silence is white	black
5	vivid	saturated, bright colour from the sounds: hue = which layers sound (notes red, beat green, high hits blue, drones violet, as a weighted mean on the colour circle), brightness = how much sounds, kept deep (8 % in silence, at most 55 %) so the white ink reads	white; every flock coloured by its voice — hue = its height = its drone's pitch (low red … high violet), saturation = its order = its harmonicity (scattered pale, aligned pure); spread ellipse filled

Logic first, also for colour: every colour must say something about the swarm or its sound. Notes and beats are events and colour when they happen. A drone sounds almost whenever there are flocks, so it colours only when it changes — a voice appearing or swelling (a flock forming, growing, merging) — not by a fixed lower weight. A flock's colour is its voice, not its number; and the vertical axis means pitch everywhere, in the sound and in the cmy map. Stills (vivid / cmy): rain = dark red / pink haze; flocks forming = blue / bands of magenta, cyan and yellow at their heights; several flocks = green / cyan bands; one groove = teal / cyan with yellow where the flock sings.