Our household has been invaded.

It all started one gray Saturday morning, when my husband left the house promising to return with a surprise. He came back with an Atari video computer system.

You've seen the bright, colorful holiday ads, the whole family crowded around the tube-turned-electronic-arcade. Unless you have children in the house (we don't) you may not have paid much attention. I didn't.

But for those of you who are pondering the purchase of similar video systems as Christmas gifts, let this serve as a warning: Your life style will never be the same again.

Since joining the computer-game age, we have:

* Developed eyestrain and headaches.

* Suffered from what we call "Atari hands" (it is not a sedentary hobby).

* Had more than the normal amount of company just "drop by."

* Replaced backgammon with a new "common interest" (meaning that most of the time I watch him play).

The day Willie hooked up the switch box to our family-room TV set, I wondered why an otherwise sane, 37-year-old man would spend hard-earned cash (about $130 if you shop around, as much as $200 if you don't) on this kind of electronic gadgetry. In my job as an editor, I complained, I look at a video-display terminal all day. All I need is to come home to the same thing. But before I could say "Star Wars," he was playing his first game of Space Invaders. "Tramp, tramp, tramp, tramp; tramp tramp, tramp tramp. Bliiiiiiiiiiiiiiiipp!" Our family room had become a science-fiction movie set.

In six years of marriage, my most vigorous competition for my husband's time has been football. I have scheduled meals around football, household and gardening chores around football, shopping trips around football, vacation plane reservations around the opening day of the season. Football addiction hardly touches that of Space Invaders.

From the beginning, traffic picked up in our family room as he introduced neighbors (children and adults) to his new hobby. One buddy dropped by at 8 o'clock one evening -- ostensibly to watch a World Series game -- and stayed until after 3 a.m.

The Space Invaders instruction booklet informed us that a score of 9,999 is the highest that can be displayed on the screen. So naturally, Willie set out to attain it (and eventually did, 1,000 by 1,000, week by week). He kept a running tab of his highest scores, sharing this information with me on a near hourly basis.

One night I found a note on the refrigerator door: "New high, 4,950." A few days later, "Space Invaders update: old high 4,950, new high 6,445."

At the same time he was moaning about headaches that struck him like one of the little bullets shot at the "invaders." Little orange things tramped through his dreams. I suggested a lighter schedule. "Why not play every other day?" He agreed.

But by far the worst pain suffered is "Atari hand." It occurs when you get into the 5,000 score range, the little invaders coming at a super rapid pace. Your weapon won't shoot fast enough. Your shields have been wiped out. They are coming faster, faster, FASTER, FASTER! To the right goes the right hand; bang, bang, shoots the left hand. Sweat is building on palms . . . 6,000 reads the score. Your left thumb is aching, may slip its joint any second . . . 7,000, 7,500, 8,000 . . . 9,999 on the electronic horizon. The score is building up; your endurance is about to break. The dog sits up on her hind legs, aware that something momentous is about to happen. Then "BOOM." Invaders hit the ground. Only 8,950.

Backgammon never worked us this hard. And don't say no one warned you.