 CONSTANT: terrain-vertex-row-length $[ 512 1 + 2 * ]
 
 TUPLE: player
-    location yaw pitch velocity ;
+    location yaw pitch velocity velocity-modifier ;
 
 TUPLE: terrain-world < game-world
     player

    [ dx>> MOUSE-SCALE * look-horizontally ]
    [ dy>> MOUSE-SCALE * look-vertically ] 2bi ;

:: handle-input ( world -- )
    world player>> :> player
    read-keyboard keys>> :> keys
    key-w keys nth [ player walk-forward ] when 
    key-s keys nth [ player walk-backward ] when 
    key-a keys nth [ player walk-leftward ] when 

    GL_DEPTH_TEST glEnable
    GL_TEXTURE_2D glEnable
    GL_VERTEX_ARRAY glEnableClientState
    PLAYER-START-LOCATION 0.0 0.0 { 0.0 0.0 0.0 } { 1.0 1.0 1.0 } player boa >>player
    <perlin-noise-table> 0.01 0.01 <scale> { 512 512 } perlin-noise-image
    [ >>sky-image ] keep
    make-texture [ set-texture-parameters ] keep >>sky-texture
