feat(patterns): add icicles blizzard and rime winter effects

Co-authored-by: Cursor <cursoragent@cursor.com>

src/patterns/rime.py

@@ -0,0 +1,72 @@
+import random
+import utime
+
+
+class Rime:
+    """Slow frost build-up on a chilly background — gentle random brightening then decay."""
+
+    def __init__(self, driver):
+        self.driver = driver
+
+    def run(self, preset):
+        colors = preset.c if preset.c else [(220, 235, 255), (255, 255, 255), (185, 220, 255)]
+        num = self.driver.num_leds
+        if num <= 0:
+            while True:
+                yield
+            return
+
+        # n1: spawn tendency (like twinkle upper range)
+        chill = max(1, min(255, int(preset.n1) if int(preset.n1) > 0 else 36))
+        # n2: decay per refresh (subtract from glow buffer)
+        melt = max(1, min(255, int(preset.n2) if int(preset.n2) > 0 else 12))
+        # n3: how many LEDs can flash brighter per refresh (cap)
+        spark_cap = max(1, min(num, int(preset.n3) if int(preset.n3) > 0 else 3))
+
+        glow = [0] * num
+        last = utime.ticks_ms()
+
+        while True:
+            d_ms = max(1, int(preset.d))
+            now = utime.ticks_ms()
+            if utime.ticks_diff(now, last) >= d_ms:
+                base_bg = preset.background_or(colors)
+                bg = self.driver.apply_brightness(base_bg, preset.b)
+
+                for i in range(num):
+                    if glow[i] > melt:
+                        glow[i] -= melt
+                    else:
+                        glow[i] = 0
+
+                spawned = 0
+                tries = spark_cap + num // 8
+                for _ in range(tries):
+                    if spawned >= spark_cap:
+                        break
+                    if random.randint(0, 255) >= chill:
+                        continue
+                    j = random.randint(0, num - 1)
+                    glow[j] = min(255, glow[j] + random.randint(80, 200))
+                    spawned += 1
+
+                palette = colors
+                for i in range(num):
+                    g = glow[i]
+                    fg = palette[i % len(palette)]
+                    hi = self.driver.apply_brightness(fg, preset.b)
+                    mix = max(0, min(255, g))
+                    self.driver.n[i] = (
+                        (hi[0] * mix + bg[0] * (255 - mix)) // 255,
+                        (hi[1] * mix + bg[1] * (255 - mix)) // 255,
+                        (hi[2] * mix + bg[2] * (255 - mix)) // 255,
+                    )
+
+                self.driver.n.write()
+                last = utime.ticks_add(last, d_ms)
+
+                if not preset.a:
+                    yield
+                    return
+
+            yield