Simplify the API

README.org

@@ -11,38 +11,36 @@ on Linux and macOS.
 
 ** API
 
+High-level API:
+- ~F _display width‿height~ creates a window of the given dimensions
+  and displays its left operand. ~F~ should be a function returning a
+  color as an RGB triplet in the (0,1) range, and taking a list of two
+  elements ~x‿y~, where ~x~ and ~y~ are the pixel coordinates.
+
+Low-level API:
 - ~OpenWindow w‿h‿t~ opens a window of width ~w~ and height ~h~, with
   title ~t~. Returns a window handle.
 - ~CloseWindow w~ closes a window given its handle ~w~.
 - ~F _render w~ runs the function ~F~ at each coordinate of the window
-  ~w~ and set the corresponding pixel color. ~F~ should be a function
-  returning a color as an RGB triplet in the (0,1) range, and taking a
-  list of three elements ~x‿y‿t~, where ~x~ and ~y~ are the pixel
-  coordinates and ~t~ is the time.
+  ~w~ and set the corresponding pixel color. ~F~ is a function with
+  the same arguments as for ~_display~.
 
 ** Example
 
 See [[./example.bqn][example.bqn]].
 
 #+begin_src bqn
-f←•Import "fenster.bqn"
+f←•Import"fenster.bqn"
 
 size←500
 
-w←f.OpenWindow size‿size‿"bqn-fenster example"
-
-Rainbow←{𝕊x‿y‿t:
+Rainbow←{𝕊x‿y:
   x‿y↩x‿y÷size
-  t↩(100|t)÷100
   h←(x+y)÷2
   f.HSVtoRGB⟨360×h,1,1⟩
 }
 
-Rainbow f._render w
-
-•Delay 3
-
-f.CloseWindow w
+Rainbow f._display size‿size
 #+end_src
 
 [[./example.png]]