+Instead of storing voxels in dumb [X * Y * Z] array, dynamically
+partitioned [[https://en.wikipedia.org/wiki/Octree][octree]] is used to compress data. Press "r" key anywhere in
+the scene to raytrace current view through compressed voxel
+datastructure.
+
+** Conway's Game of Life
+The Game of Life, also known simply as Life, is a cellular automaton
+devised by the British mathematician John Horton Conway in 1970.
+
++ https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life
+ + Game rules:
+ + 2 cell states: alive / dead
+ + Each cell sees 8 neighboring cells.
+ + If alive cell neighbors count is 2 or 3, then cell survives,
+ otherwise it dies.
+ + Dead cell becomes alive if neighbors count is exactly 3.
+
+[[file:screenshots/life.png]]
+
+Current application projects 2D game grid/matrix onto three
+dimensional space. Extra dimension (height) is used to visualize
+history (previous iterations) using glowing dots suspended in space.
+
+Usage:
+| key | result |
+|--------------------------------+--------------------------------------|
+| mouse click on the cell (cell) | toggles cell state |
+| <space> | next iteration |
+| ENTER | next iteeration with the history |
+| "c" | clear the matrix |
+
+** Text editors
+[[file:screenshots/text editors.png]]
+
+Initial test for creating user interfaces in 3D and:
++ window focus handling
++ picking objecs using mouse
++ redirecting keyboard input to focused window
+
+
+Window focus acts like a stack.
+
+When window is clicked with the mouse, previously focused window (if
+any) is pushed to the focus stack and new window receives focus. Red
+frame appears around the window to indicate this.
+
+When ESC key is pressed, window focus is returned to previous window
+(if any).
+
+When any window is focused, all keyboard input is redirected to that
+window, including cursor keys. To be able to navigate around the world
+again, window must be unfocused first using ESC key.
+
+
++ TODO:
+ + Improve focus handling:
+ + Perhaps add shortcut to navigate world without exiting entire
+ stack of focus.
+ + Possibility to retain and reuse recently focused elements.
+ + Store user location in the world and view direction with the
+ focused window. So that when returning focus to far away object,
+ user is redirected also to proper location in the world.
+ + Possibility to store recently visited locations in the world and
+ return to them.
+** Mathematical formulas
+[[file:screenshots/mathematical formulas.png]]
+
++ TODO: instead of projecting 2D visualizations onto 3D space,
+ visualize some formula using all 3 dimensions avaliable.
+** Sinus heightmaps and sphere
+[[file:screenshots/sinus heightmaps and sphere.png]]
+
+Simple test scene. Easy to implement and looks nice.