Meteor Shower

REBOL [title: "Meteor Shower"]

alert "Left arrow moves character left! Right arrow moves character right!"
random/seed now/time   speed: 5   score: 0
view center-face layout [
    size 600x440   backdrop reblue   across
    at 270x0 text "SCORE:"  t: text bold 100 (form score)
    at 280x20  y: btn 50x20 64.64.64
    at 280x420 z: btn 50x20 green
    key keycode [left] [z/offset: z/offset - 10x0  show z]
    key keycode [right]  [z/offset: z/offset + 10x0  show z]
  	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 + 5
			speed: speed + 1
			if speed > 10 [
			speed: speed - 1
        ]
        if within? z/offset (y/offset - 50x0) 100x20 [
            y/offset: as-pair (random 550) 20   show y
            score: score - 5
			speed: speed - 1
        ]
        t/text: (form score)  show t
    ]]]]
]