diff --git a/src/aphorisms/eight.clj b/src/aphorisms/eight.clj
index bac9416..8d26fa2 100644
--- a/src/aphorisms/eight.clj
+++ b/src/aphorisms/eight.clj
@@ -37,6 +37,6 @@
   :setup setup
   :update update-state
   :draw draw-state
-  :renderer :p3d
+  :renderer :opengl
   :features [:keep-on-top :no-bind-output]
   :middleware [qm/pause-on-error qm/fun-mode])
diff --git a/src/aphorisms/eighteen.clj b/src/aphorisms/eighteen.clj
new file mode 100644
index 0000000..8109393
--- /dev/null
+++ b/src/aphorisms/eighteen.clj
@@ -0,0 +1,111 @@
+(ns aphorisms.eighteen
+  (:require [quil.core :as q]
+            [quil.middleware :as qm]
+            [thi.ng.geom.vector :as v]
+            [thi.ng.geom.rect :as r]
+            [thi.ng.geom.core :as g]
+            [thi.ng.math.core :as m]))
+
+(def bounds (r/rect 500))
+
+(defn arc [c start end]
+  {:c c
+   :start start
+   :end end})
+
+(defn radians [arc start-or-end]
+  (g/angle-between (:c arc) (get arc start-or-end)))
+
+(defn radius [arc]
+  (m/mag (m/- (:c arc) (:start arc))))
+
+(comment
+  (def tmp (arc (v/vec2 0 0) (v/vec2 -100 0) (v/vec2 0 100)))
+
+  (radians tmp :start) ;; => 3.141592653589793
+  (radians tmp :end) ;; => 1.5707963267948966
+  (radius tmp) ;; => 100.0
+
+  )
+
+;; a random sample inside bounds separates the space into four parts
+;; i want to get the biggest part
+
+(identity bounds)
+;; => {:p [0.0 0.0], :size [500.0 500.0]}
+
+(g/random-point-inside bounds)
+;; => [3.722300840831416 95.03615495022028]
+
+
+(defn subdivide-at [rect p]
+  [(r/rect (:p rect) p)
+   (r/rect (v/vec2 (:x p) (r/bottom rect)) (v/vec2 (r/right rect) (:y p)))
+   (r/rect (v/vec2 (r/left rect) (:y p)) (v/vec2 (:x p) (r/top rect)))
+   (r/rect (v/vec2 (:x p) (:y p)) (v/vec2 (r/top rect) (r/right rect)))])
+
+(let [division bounds
+      p (g/random-point-inside division)
+      biggest-division (->> (subdivide-at bounds p)
+                            (sort-by (comp - g/area))
+                            (first))]
+  [p
+   biggest-division
+   (-> (g/translate biggest-division (m/- p))
+       (g/scale 0.66)
+       (g/translate p))])
+
+(defn reset-state [& _]
+  (let [p (g/random-point-inside bounds)
+        start (m/+ p (v/randvec2 50))
+        end (-> (g/translate start (m/- p))
+                (g/rotate (rand m/HALF_PI))
+                (g/translate p))]
+  {:arcs [(arc p start end)]}))
+
+(defn setup []
+  (q/frame-rate 1)
+  (q/rect-mode :center)
+  (q/ellipse-mode :center)
+  (q/color-mode :hsb 360 100 100)
+  (q/background 10 20 100)
+  (reset-state))
+
+(defn update-state [state]
+  state)
+
+(defn draw-state [state]
+  (q/background 10 20 100)
+  (q/stroke 200 80 100)
+  (q/no-fill)
+  (doseq [{[x y] :c :as arc} (:arcs state)
+          :let [start (radians arc :start)
+                end (radians arc :end)]]
+    (q/ellipse x y 5 5)
+    (q/line (:c arc) (:start arc))
+    (q/line (:c arc) (:end arc))
+    (q/arc x y (radius arc) (radius arc) (min start end) (max start end))))
+
+(defn origin-at-bottom-left
+  "Make processing and thi.ng use the same coordinate system, with the orgin
+  at the bottom left."
+  [options]
+  ;; note that this usually doesn't make any difference, but we're using
+  ;; "r/bottom" and "r/top" here soooo… let's be consistent
+  (update options :draw (fn [draw]
+                          (fn [& args]
+                            (q/translate 0 (get-in options [:size 1]))
+                            (q/scale 1 -1)
+                            (apply draw args)))))
+
+#_:clj-kondo/ignore
+(q/defsketch eighteen
+  :title "Eighteen"
+  :size (:size bounds)
+  :settings #(q/pixel-density (q/display-density))
+  :setup setup
+  :update update-state
+  :mouse-pressed reset-state
+  :draw draw-state
+  ;; :renderer :p2d
+  :middleware [qm/pause-on-error qm/fun-mode origin-at-bottom-left])
diff --git a/src/aphorisms/eleven.clj b/src/aphorisms/eleven.clj
index 211abf3..043bf90 100644
--- a/src/aphorisms/eleven.clj
+++ b/src/aphorisms/eleven.clj
@@ -41,6 +41,10 @@
           (apply q/vertex pt)))
       (q/end-shape :close))))
 
+(defn settings []
+  (q/pixel-density (q/display-density))
+  (q/smooth 2))
+
 (q/defsketch eleven
   :title "Eleven"
   :size [500 500]
diff --git a/src/aphorisms/nineteen.clj b/src/aphorisms/nineteen.clj
new file mode 100644
index 0000000..fddc936
--- /dev/null
+++ b/src/aphorisms/nineteen.clj
@@ -0,0 +1,42 @@
+(ns aphorisms.nineteen
+  (:require [quil.core :as q]
+            [quil.middleware :as qm]
+            [thi.ng.geom.rect :as r]
+            [thi.ng.geom.core :as g]
+            [thi.ng.math.core :as m]))
+
+(def bounds (r/rect 500 500))
+
+(defn setup []
+  (q/frame-rate 1)
+  (q/rect-mode :center)
+  (q/ellipse-mode :center)
+  (q/color-mode :hsb 360 100 100)
+  (q/background 10 20 100)
+  {})
+
+(defn update-state [state]
+  state)
+
+(defn draw-state [state]
+  (let [canvas (g/scale (:size bounds) 0.92)]
+    (q/background 40 10 100)
+    (q/no-fill)
+    (q/with-translation [250 250]
+      (doseq [i (range 100)
+              :let [norm (* 0.01 i)
+                    x (m/map-interval i [0 99] [(* -0.5 (:x canvas)) (* 0.5 (:x canvas))])
+                    x-off (m/map-interval (q/sin (* norm q/PI)) [-1 1] [-50 50])]]
+        (q/line (+ x x-off) -20 (+ x x-off) 20)))))
+
+
+#_:clj-kondo/ignore
+(q/defsketch eighteen
+  :title "Eighteen"
+  :size (:size bounds)
+  :settings #(q/pixel-density (q/display-density))
+  :setup setup
+  :update update-state
+  :draw draw-state
+  ;; :renderer :p2d
+  :middleware [qm/pause-on-error qm/fun-mode])
diff --git a/src/aphorisms/sixteen.clj b/src/aphorisms/sixteen.clj
new file mode 100644
index 0000000..6f62d54
--- /dev/null
+++ b/src/aphorisms/sixteen.clj
@@ -0,0 +1,67 @@
+(ns aphorisms.sixteen
+  (:require [thi.ng.math.core :as m]
+            [thi.ng.geom.core :as g]
+            [thi.ng.geom.vector :as v]
+            [thi.ng.geom.line :as l]
+            [thi.ng.math.noise :as n]
+            [thi.ng.geom.rect :as r]
+            [quil.core :as q]
+            [quil.middleware :as qm]))
+
+(defn setup []
+  (q/frame-rate 30)
+  (q/color-mode :hsb 360 100 100)
+  (q/rect-mode :center)
+  (q/ellipse-mode :center)
+  (q/background 180 10 90)
+  {})
+
+
+(defn update-state [state]
+  state)
+
+(defn grid [r divisions]
+  (->>
+   (g/subdivide r {:num divisions})
+   (map (comp v/vec2 (juxt r/left r/top)))
+   #_(take (inc (* divisions divisions)))))
+
+(def grid-points
+  (->> (g/subdivide (r/rect [72 72] [428 428]) {:num 25})
+       (map g/edges)
+       (apply concat)
+       (apply concat)
+       (dedupe)
+       (map v/vec2)))
+
+(defn line-crossing [v length]
+  (l/line2 (m/- v (v/vec2 [(* length 0.5) 0]))
+           (m/+ v (v/vec2 [(* length 0.5) 0]))))
+
+(defn draw-state [state]
+  (q/background 180 10 90)
+  (q/no-fill)
+  (doseq [[p1 p2 :as pt] grid-points
+          :let [length (m/map-interval p2 [72 428] [3 18])
+                [[x1 y1] [x2 y2]] (-> (line-crossing pt length)
+                                      (g/translate (m/- pt))
+                                      (g/rotate (+ m/QUARTER_PI
+                                                   (* (n/noise2 (* 0.52 p1) (* 0.02 p2)) m/QUARTER_PI)))
+                                      (g/translate pt)
+                                      (g/vertices))]]
+    (q/line x1 y1 x2 y2)
+    (q/stroke-cap :round)
+    (q/stroke-weight 1.2)
+    (q/stroke 340 20 90)))
+
+#_:clj-kondo/ignore
+(q/defsketch sixteen
+  :title "Sixteen"
+  :size [500 500]
+  :settings #(q/pixel-density (q/display-density))
+  :setup setup
+  :update update-state
+  :draw draw-state
+  :renderer :p2d
+  :features [:keep-on-top :no-bind-output]
+  :middleware [qm/pause-on-error qm/fun-mode])