Mastering Space Invaders: Aim, Cover, and Bonus UFO

Space Invaders looks like it’s about firing fast. It’s not. Taito’s 1978 arcade landmark is about aim discipline, bunker management, and reading the speed-up curve that comes from the game’s CPU running faster as fewer aliens remain on screen. Mastering Space Invaders means firing one bullet at a time accurately, keeping your bunkers intact long enough to matter, and hitting the bonus UFO every time it crosses. The score gap between casual and elite is enormous.

The single-bullet rule

Space Invaders only allows one player bullet on screen at a time. Press fire, and the next shot can’t be fired until the previous bullet either hits something or exits the top of the screen. This single rule shapes every strategic choice in the game.

Beginners spam the fire button and get one shot every couple of seconds because their bullets are constantly traveling up the long empty space. Skilled players time shots so the bullet lands quickly and the next is available immediately. The shot rhythm matters more than the trigger speed.

The optimization: shoot when your target is close to your column, not when it’s at the far side of the screen. Closer targets mean faster bullet travel time, which means faster next-shot availability.

The acceleration mystery

Aliens move faster as more are destroyed. This was famously a bug in the original Taito hardware — the CPU couldn’t update all 55 alien sprites at full speed, so the apparent move rate was slower with more aliens on screen. As you killed aliens, the CPU had less work to do, and the remaining aliens moved faster.

Designer Tomohiro Nishikado realized the bug improved the game’s tension and kept it. Now the speed-up is intentional in every faithful Space Invaders port. The last alien moves much faster than the first 54 did.

Strategy implication: think about which alien to leave for last. The final alien is fast and unpredictable. Most players prefer leaving a low-value bottom-row alien, which is slower-moving in absolute screen terms but harder to predict.

Aim discipline

Each shot has to count. Two principles:

1. Don’t fire while moving. The bullet inherits your ship’s position only at fire moment; if you keep moving, you can fire into empty space because your target moved.
2. Lead the shot. Aliens move sideways at consistent speeds. Predict where the alien will be by the time your bullet arrives.

The lead is more important at distance. Aliens at the top of the screen require leading because your bullet takes a full second to reach them; by then, the alien has moved several columns. Aliens at the bottom of the screen are essentially point-blank — fire when your column matches their column.

The point values by row

From bottom to top, the alien rows are worth (in the standard Taito values):

• Bottom two rows (small invaders): 10 points each.
• Middle two rows (medium invaders): 20 points each.
• Top row (large invaders): 30 points each.

Higher rows are worth more, but they’re farther from your ship and require longer-travel bullets. Bottom rows are easier targets but score less.

The score-per-shot optimization: hit top-row aliens when they’re still high, because that’s when they’re worth most relative to your shot cost. As aliens descend, their position improves for shooting but their point value stays the same.

The bonus UFO

A red UFO crosses the top of the screen periodically. It’s worth variable points — 50, 100, 150, 200, or 300, depending on a specific condition.

The condition is famous and was figured out by competitive players: the UFO’s score depends on your shot count. Every 15 shots cycles the UFO scoring. Specifically:

• On certain shot counts, the UFO is worth 300 points (the maximum).
• Most shots produce lower UFO values (50, 100, 150, or 200).

Elite players count shots and time their UFO kills to the high-value shot positions. The exact shot count for the 300-point UFO is documented in competitive Space Invaders communities, and is part of why high-score runs require deliberate shot management, not spam firing.

Bunker management

The four bunkers between your ship and the aliens are destructible cover. Alien bullets erode them on impact, as do your own bullets if they pass through. Bunkers protect you from alien fire but only until they degrade past the point of usefulness.

Two bunker strategies:

1. Preserve and use: hide behind bunkers when needed, fire only between bunkers from open positions.
2. Carve and hide: deliberately shoot through a bunker to create a sniper notch, then fire from inside it.

The carve-and-hide approach is popular in high-level play. A bunker with a vertical notch lets you fire upward without exposing your ship to most alien fire angles. The notch eventually erodes, but it buys significant time.

Don’t carve through your bunker prematurely — alien fire will widen the gap quickly, and bunkers degrade faster than they can be repaired (they don’t repair at all).

The descending aliens problem

The aliens advance one row downward each time they reach the screen edge. If they reach the bottom of the screen, the game ends regardless of your remaining lives. The acceleration combined with descent means the late-stage game is a race: kill the last aliens before they reach your row.

The strategic priority shifts based on alien position. Early in a wave (aliens at the top), score-per-shot matters — pick off high-value top-row aliens. Late in a wave (aliens near the bottom), survival matters — kill whatever is closest before it reaches the bottom.

The two-column squeeze

A common death is being squeezed between aliens at the screen edge. Aliens move sideways before dropping; if you’re at the same edge they’re approaching, you can be hit by an alien bullet from short range with little reaction time.

Solution: stay near the center of the screen for the early game. As aliens approach an edge, move to the opposite edge. The center gives equal escape distance both ways, plus access to most of the bunker line.

Counting shots

Top-tier Space Invaders play involves counting your shots. The bonus UFO timing depends on shot count, and certain alien patterns are more efficient to clear if you know your shot budget.

This is tedious but rewards score. Casual players don’t need to count. Players going for personal bests should.

The 56th alien

Space Invaders has 55 aliens per wave (5 rows of 11 columns) plus the bonus UFO. The 55th alien — the very last one — is famously fast. Some players exploit the speed to hit it at maximum point value during a UFO crossing for combined bonus.

Most players just want to kill the last alien before it reaches the bottom of the screen. The wave clears, the next wave starts one row lower than the last, and the cycle continues with progressive difficulty.

For more on Space Invaders’ history and cultural impact, see our Space Invaders history piece. The Space Invaders Wikipedia article covers the original 1978 release and its many ports.

Practice approach

Three drills:

1. Single-shot accuracy: fire one bullet, wait for it to land or miss, fire the next. Trains shot discipline and removes spam-firing habit.
2. UFO sniper: ignore all aliens, wait for the UFO, and practice hitting it consistently with one bullet per crossing.
3. Bunker carving: deliberately carve a notch in a bunker on wave 1 and play from inside it. Practices position discipline.

The combined drills build the habits that separate intermediate from elite players.

Frequently asked questions

Why do the aliens speed up in Space Invaders?

Originally a hardware bug — the CPU couldn’t render 55 sprites at full speed, so they moved slower with more aliens on screen. As aliens were destroyed, the CPU had less work, and the remaining ones moved faster. Designer Tomohiro Nishikado kept the behavior because it improved game tension.

How many bullets can I have on screen in Space Invaders?

One. Only one player bullet can exist on screen at a time. The next shot can’t be fired until the current bullet either hits a target or exits the top of the screen. Shot timing is the single most important skill.

How does the bonus UFO scoring work?

The UFO’s point value depends on your shot count — every 15 shots cycles through values 50, 100, 150, 200, and 300. Elite players count shots and time UFO kills to land on the 300-point positions for maximum score.

How much are different alien rows worth in Space Invaders?

Bottom two rows: 10 points each. Middle two rows: 20 points each. Top row: 30 points each. Higher rows are worth more but require longer-travel bullets, so score-per-shot vs hit-rate is a trade-off in shot selection.

Should I shoot through my bunker in Space Invaders?

Maybe — the “carve and hide” strategy involves shooting a vertical notch through a bunker and firing from inside it. The notch protects against most alien fire while letting you shoot upward. Don’t carve prematurely; alien fire will widen the gap quickly.

The takeaway

Space Invaders is a shot-discipline game. One bullet at a time, every shot counted, UFOs timed to shot count for maximum bonus, and bunkers carved for cover. The game accelerates from a controlled puzzle into a survival sprint as you progress. Master these layers and your scores climb. For a different kind of one-button arcade survival game, the Chrome Dino game swaps shot management for jump timing.