rename assets/epaper.lua to assets/boot.lua

assets/boot.lua

@@ -0,0 +1,55 @@
+local math = require('math')
+local paper = require('paper')
+
+paper.init()
+paper.set_rotation("portrait")
+paper.clear()
+
+local width = paper.get_width()
+local height = paper.get_height()
+
+print(
+  'width: ' .. width,
+  'height: ' .. height
+)
+
+-- easing functions taken from https://easings.net/
+
+function ease_in_sine(x)
+  return 1 - math.cos(x * math.pi / 2)
+end
+
+function ease_in_out_sine(x)
+  return -(math.cos(math.pi * x) - 1) / 2
+end
+
+--
+-- actual sketch follows below
+--
+
+local x = width / 2
+local max_radius = 128
+local min_radius = max_radius / 6
+local padding = max_radius
+local max_color = 0xDD
+local min_color = 0x33
+local steps = 72
+
+-- background
+paper.fill_rect(0, 0, width, height, 0x22)
+
+-- sketch
+for i = 1, steps do
+  local n = i / steps
+  local e1 = ease_in_sine(n)
+  local e2 = 1 - ease_in_out_sine(ease_in_sine(n))
+  local color = math.floor(max_color - (max_color - min_color) * e2)
+  paper.fill_circle(
+    x + math.sin((math.pi * 2) / n) * 32 * e1,
+    padding + (height - max_radius - padding * 2) * e1,
+    min_radius + (max_radius - min_radius) * e1,
+    color
+  )
+end
+
+paper.update()