Star Defense

How to play

Your ship sits on the bottom edge and moves left and right, nothing else. Above it, thirty-two attackers hang in a block four rows deep and eight columns wide. The block slides sideways as one piece; when its leading edge touches a wall it reverses direction and drops fourteen pixels closer to you. It never retreats. The game ends when your last ship is destroyed or when the lowest attacker reaches your line — whichever happens first, and on the higher ranks it is usually the second.

You clear a wave by destroying all thirty-two. Doing that rebuilds the block at the top, restores the shields, awards a bonus that grows with the wave number, and starts everything moving faster. The wave counter is the number worth watching: score follows almost automatically from how deep you get, because the point values per attacker never change.

Those values reward the back of the formation. The top row is worth 60 points a kill, then 45, then 30, and the front row nearest you is worth 15. That is the opposite of what your instincts want, because the front row is the one about to land on you, and resolving that tension is most of the game.

Controls

• Desktop: ← → or A D to move, Space to fire, P to pause. Space also launches the first game and restarts after a loss.
• Phone or tablet: drag anywhere on the board and the ship follows your finger; lift without dragging and that counts as a shot. Page scrolling is suppressed while your finger is on the board.
• Two bolts maximum: only two of your shots can exist at once. A third press is ignored until one of the first two connects or leaves the top of the screen.

Kill the flanks first, and other things that actually work

The single most useful thing to know is that the formation accelerates as it thins. Speed is multiplied by the fraction of the wave you have already cleared, so the same block that crawled at the start is sprinting by the time four attackers remain. This has a practical consequence: the last few kills are the hardest part of every wave, and you should spend the easy early seconds building an advantage rather than admiring your accuracy.

The advantage worth building is a narrow formation. Clear the outermost column first, then the next one in, working from the edges toward the middle. A block that is two columns wide has to travel much further before it touches a wall, which means it drops rows far less often. Players who clear from the middle outward end up with two survivors at opposite edges, each triggering a drop almost immediately — the formation then descends about twice as fast for the same number of kills.

Second habit: aim where the target will be, not where it is. Your bolt takes roughly two hundred milliseconds to cross the board, and the formation is always moving sideways during that flight. Lead it. The fix is simple once you notice the problem, and most opening-wave misses come from firing at a target that has already left.

Third: your own shots destroy shield blocks. The shields are not selective cover, they are just matter, and a bolt fired from directly underneath one will eat a hole in your own protection. Position yourself in the gaps between bunkers to fire, and duck behind a bunker to survive. Using a shield as a firing position is the fastest way to have no shields left by wave three.

Fourth: watch the bomb count, not the bombs. Cadet allows three enemy bombs in the air at a time, Pilot four, Ace five. When the screen is already at its limit, nothing new can be dropped on you, which makes the moment right after a volley the safest window to move across open ground.

Where this shape of game comes from

The arcade genre now called the fixed shooter — a player craft locked to one axis at the bottom of the screen, enemies descending in formation — was defined by a cabinet Taito released in Japan in 1978. Its famous escalating tempo was not designed as a difficulty curve at all: the hardware simply drew each remaining sprite faster as fewer of them were left on screen, and the accelerating march turned out to be so effective that every game in the genre since has copied it on purpose. Ours does the same thing deliberately, in the movement code, because it is genuinely good design.

Namco's Galaxian followed in 1979 and added attackers that peeled out of the formation to dive, which split the genre into two lineages that still exist. Star Defense stays on the older branch: the block holds its shape, and the pressure comes from geometry and tempo rather than from unpredictable flight paths.

Everything you are playing here is our own code, written for this site. The board is a fixed 640 by 520 internal grid scaled to your display, the loop is delta-timed so the formation crosses the screen in the same number of seconds on a 60 Hz laptop and a 144 Hz monitor, and every projectile moves in sub-steps of at most six pixels so a fast bolt can never skip past a target between frames. Random choices — which column drops the next bomb, the jitter on the firing interval — come from your browser's cryptographic random source.

Questions players ask