Randomize base jitter instead of a fixed +1/-1 alternation

Fixed +1/-1 alternation read as too mechanically regular -- a
predictable back-and-forth. Now picks randomly from {-1, 0, 1} per
burst state via random.star (random.number(0, 2) - 1, since
random.number requires a non-negative minimum).

subwave_nowplaying.star

@@ -12,6 +12,7 @@ load("cache.star", "cache")
 load("time.star", "time")
 load("animation.star", "animation")
 load("filter.star", "filter")
+load("random.star", "random")
 
 DEFAULT_STATION_URL = ""
 NOWPLAYING_TTL = 20
@@ -478,19 +479,18 @@ def _glitch_jitter(zoom):
     pause = _glitch_hold(render.Box(width = ART_SLOT, height = ART_SLOT), GLITCH_PAUSE_TICKS)
 
     sequence = []
-    state_index = 0
     for cycle_index in range(GLITCH_REPEATS):
         for top1, h1, shift1, hue1, top2, h2, shift2, hue2 in _glitch_states_for_cycle(cycle_index):
             # The art itself nudges along with the bands, not just the
             # bands moving over a static image. Capped to +-1px -- a
             # full-frame shift reads very differently than a thin band
-            # shifting, so it stays subtle. Alternates +1/-1 by position
-            # in the sequence rather than deriving from shift1/shift2:
-            # several pool entries have those nearly or exactly
-            # cancel out (e.g. -2 and 2), which silently zeroed out the
-            # jitter in about half the states.
-            base_shift = 1 if state_index % 2 == 0 else -1
-            state_index += 1
+            # shifting, so it stays subtle. Randomized rather than a fixed
+            # alternating +1/-1 (which read as too mechanically regular,
+            # a predictable back-and-forth) or derived from shift1/shift2
+            # (several pool entries have those nearly or exactly cancel
+            # out, e.g. -2 and 2, which silently zeroed out the jitter in
+            # about half the states).
+            base_shift = random.number(0, 2) - 1  # random.number requires min >= 0
             state = render.Stack(children = [
                 _glitch_base_jitter(zoom, base_shift),
                 # _glitch_band(zoom, top1, h1, shift1, hue1),