Catch game

Here the source of a very simple game, move your brick using the arrows to touch the falling bricks:

You can use up and down arrow to change game speed. Please notice the use of key to assign a function to a keyboard key, and keycode to use special button like the arrows:
REBOL [
title: "Catch Game"
date: 30-Apr-2010
file: %catch-game.r
author:   Nick Antonaccio
purpose: {
A tiny game to demonstrate the basics of VID.
Taken from the tutorial at http://re-bol.com
}
]
alert "Arrow keys move left/right (up: faster, down: slower)"
random/seed now/time   speed: 11   score: 0
view center-face layout [
size 600x440   backdrop white   across
at 270x0 text "Score:"   t: text bold 100 (form score)
at 280x20   y: btn 50x20 orange
at 280x420 z: btn 50x20 blue
key keycode [left] [z/offset: z/offset - 10x0   show z]
key keycode [right]   [z/offset: z/offset + 10x0   show z]
key keycode [up]   [speed: speed + 1]
key keycode [down]   [if speed >   1 [speed: speed - 1]]
box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
y/offset: y/offset + (as-pair 0 speed)   show y
if y/offset/2 > 440 [
y/offset: as-pair (random 550) 20   show y
score: score - 1
]
if within? z/offset (y/offset - 50x0) 100x20 [
y/offset: as-pair (random 550) 20   show y
score: score + 1
]
t/text: (form score)   show t
]]]
]