diff --git a/interactions.py b/interactions.py
new file mode 100644
index 0000000..4331426
--- /dev/null
+++ b/interactions.py
@@ -0,0 +1,194 @@
+#!/usr/bin/python3
+
+from math import pi, cos, sin, exp
+
+import phue, pygame, colorsys
+
+# === graph data ===
+
+# vertices as screen positions
+viewsize = 600
+shrink = 0.9
+vertices = [(viewsize*(1 + shrink*x)/2, viewsize*(1 + shrink*y)/2) for x, y in
+  [(0, 0)] + [(cos(-n*pi/5), sin(-n*pi/5)) for n in range(10)] + [(0, 0)]
+]
+
+# edges as vertex pairs. FireStar will rest on vertices 6 (A), 5 (B), 7 (C)
+vertex_adj = [
+  (0, 1), (0, 3), (0, 5), (0, 7), (0, 9),
+  (2, 8), (2, 6), (6, 10), (10, 4), (4, 8),
+  (2, 9), (2, 11), (2, 5),
+  (4, 1), (4, 9), (4, 7),
+  (6, 3), (6, 11), (6, 9),
+  (8, 5), (8, 11), (8, 1),
+  (10, 7), (10, 11), (10, 3),
+  (9, 3), (9, 5),
+  (1, 5), (1, 7),
+  (3, 7)
+]
+
+# cyclic edge adjacencies
+cyc_edge_adj = [
+  (0, 1), (1, 2), (2, 3), (3, 4), (4, 0),
+  (5, 10), (10, 11), (11, 12), (12, 6), (6, 5),
+  (6, 16), (16, 17), (17, 18), (18, 7), (7, 6),
+  (7, 22), (22, 23), (23, 24), (24, 8), (8, 7),
+  (8, 13), (13, 14), (14, 15), (15, 9), (9, 8),
+  (5, 9), (9, 19), (19, 20), (20, 21), (21, 5),
+  (4, 10), (10, 25), (25, 26), (26, 18), (18, 4),
+  (3, 15), (15, 29), (29, 28), (28, 22), (22, 3),
+  (2, 12), (12, 27), (27, 26), (26, 19), (19, 2),
+  (1, 24), (24, 25), (25, 29), (29, 16), (16, 1),
+  (0, 21), (21, 28), (28, 27), (27, 13), (13, 0),
+  (14, 11), (11, 23), (23, 20), (20, 17), (17, 14)
+]
+
+# === pygame setup ===
+
+pygame.init()
+screen = pygame.display.set_mode((viewsize, viewsize + 100))
+pygame.display.set_caption('Preview')
+font = pygame.font.Font(None, 25)
+clock = pygame.time.Clock()
+
+# === bridge setup and control ===
+
+# --- copied from firestar.py
+
+b = phue.Bridge('172.18.130.12')
+##b = None
+Nedges = 30;
+edgecode = [None] * Nedges;
+
+# The edges are numbered as in info/SSDedges.obj; enter the two-letter code for
+# the lightstrip inserted through each edge in the block below:
+
+exec(open("edgecodes.py").read())
+
+if b != None:
+  edges = [ b[code] for code in edgecode ]
+
+lasthue = 65535
+fullbright = 254
+fullsat = 254
+
+# --- control methods
+
+def set_light_hsv(e, color, hit_bridge):
+  command = {
+    'hue' : int(color[0]*lasthue),
+    'bri' : int(color[2]*fullbright),
+    'sat' : int(color[1]*fullsat)
+  }
+  if hit_bridge and b != None:
+    b.set_light(edges[e].light_id, command)
+  rgb_color = tuple(255*c for c in colorsys.hsv_to_rgb(*color))
+  pygame.draw.aaline(screen, rgb_color, vertices[vertex_adj[e][0]], vertices[vertex_adj[e][1]])
+
+# === interaction parameters ===
+
+frame_rate = 2
+
+inductance = 0.001
+
+therm_conduct = 0.001
+
+drain = False
+drain_rate = 0.1
+
+# === phase space ===
+
+charge = 12*[0]
+current = 30*[0]
+
+last_litness = 30*[float("inf")]
+change_threshold = 0.05
+
+# === main loop ===
+
+def heat_evolution():
+  for e, f in cyc_edge_adj:
+    flow = therm_conduct*(current[e] - current[f])
+    current[e] -= flow
+    current[f] += flow
+    if drain:
+      current[v] *= 1 - drain_rate
+
+def wave_evolution():
+  # use verlet integration, first updating the currents and then using the new
+  # currents to update the charges.
+  for e in range(30):
+    u, v = vertex_adj[e]
+    current[e] += inductance*(charge[u] - charge[v])
+  for e in range(30):
+    u, v = vertex_adj[e]
+    charge[u] -= current[e]
+    charge[v] += current[e]
+  if drain:
+    for v in range(12):
+      charge[v] *= 1 - drain_rate
+
+def set_wave_light(e, i):
+  litness = 1 - exp(-2*i*i)
+  hit_bridge = abs(litness - last_litness[e]) > change_threshold
+  set_light_hsv(e, (0.45 + litness*0.25, 1 - 0.5*litness*litness, litness), hit_bridge)
+  if hit_bridge:
+    last_litness[e] = litness
+
+def show_data(screen):
+  energy = 0.5*(sum(q*q for q in charge) + inductance*sum(i*i for i in current))
+  text = font.render('energy', True, (255, 255, 255))
+  screen.blit(text, (20, viewsize))
+  text = font.render(str(energy), True, (255, 255, 255))
+  screen.blit(text, (120, viewsize))
+  text = font.render('charge[0]', True, (255, 255, 255))
+  screen.blit(text, (20, 30 + viewsize))
+  text = font.render(str(charge[0]), True, (255, 255, 255))
+  screen.blit(text, (120, 30 + viewsize))
+
+if __name__ == '__main__':
+  # set up background
+  background = pygame.Surface(screen.get_size()).convert()
+  background.fill((32, 32, 32))
+  text = font.render('press [j] or [k] to pluck', True, (255, 255, 255))
+  background.blit(text, (340, viewsize))
+  text = font.render('hold [space] to drain', True, (255, 255, 255))
+  background.blit(text, (340, 30 + viewsize))
+  
+  to_light = 0
+  while True:
+    # handle events
+    for event in pygame.event.get():
+      if event.type == pygame.KEYDOWN:
+        if event.key == pygame.K_j:
+          charge[0] += 100
+          charge[11] -= 100
+        elif event.key == pygame.K_k:
+          charge[5] += 100
+          charge[7] -= 100
+        elif event.key == pygame.K_SPACE:
+          drain = True
+        pygame.draw.aaline(screen, (255, 255, 255), (0, 0), (viewsize, viewsize))
+      elif event.type == pygame.KEYUP:
+        if event.key == pygame.K_SPACE:
+          drain = False
+      elif event.type == pygame.QUIT:
+        quit()
+    
+    # clear screen
+    screen.blit(background, (0, 0))
+    
+    # show data
+    show_data(screen)
+    
+    # show state
+    for e in range(30):
+      set_wave_light(e, current[e])
+    
+    # evolve state
+    wave_evolution()
+    ##heat_evolution()
+    
+    # step
+    pygame.display.flip()
+    clock.tick(frame_rate)