The sky gradient in Skyfall isn't a background image — it's calculated every frame from how far into the 60-second round you are, interpolating between a daytime blue, a dusk orange-pink, and a starry navy. Here's roughly how that works and why we built it this way instead of just dropping in three background images and cross-fading them.
Each frame, we take the elapsed time as a fraction of the round length (0 at the start, 1 at the end) and use it to interpolate between three anchor colors in HSL space rather than RGB — HSL blends more naturally for sky-like gradients because you're mostly rotating hue and dimming lightness rather than fighting with three independent RGB channels that don't move together the way light actually does. The canvas gradient is redrawn each frame with the interpolated stops, so the sky is never a static image; it's a live function of time.
We built it this way for two reasons. First, a static background makes a round feel the same whether you're 5 seconds in or 55 — a shifting sky gives players a passive, ambient sense of urgency without adding another HUD element competing for attention. You don't have to glance at a timer to feel that the round is ending; the world around the birds tells you. Second, procedural skies mean zero image assets to load, which keeps the whole game fast even on a slow connection — there's nothing to fetch, decode, or cache for the background, just math running every frame.
The stars that fade in during the last third of a round are just randomly placed points with a flicker applied via a sine wave on their opacity, offset per-star so they don't all pulse in sync. It's a small trick, but it's the difference between a night sky that reads as static wallpaper and one that reads as alive. Getting the flicker timing right — slow enough to read as twinkling, fast enough not to look like a bug — took more tuning than the rest of the sky system combined.