Space Invaders
Hold the line as the formation drops row by row. Made by Dave Kerr.
Left and right arrows to move. Space to fire. Enter to start or restart.
How to play
- A grid of invaders marches sideways and drops a row each time it reaches an edge.
- Move your ship along the bottom and shoot them before they reach you.
- Their bombs fall constantly, so standing still is rarely safe.
- Clear the whole formation to move to a faster wave.
Playing it better
- Clear the outside columns first. It gives the formation more room to travel and buys time before it drops.
- Fire on the move. Stopping to line up a shot is what gets you hit.
- Track the lowest invader, not the closest one. It sets your real deadline.
- The formation speeds up as it thins out, so the last few are always the hardest.
About Space Invaders
Space Invaders is the game that invented the shape of the arcade era: one gun at the bottom, a wall of enemies at the top, and a countdown that gets louder as it gets closer. This open source HTML5 version by Dave Kerr is a clean rewrite for the browser under the MIT licence, keeping the marching formation, the accelerating pace and the bombs falling from above.
The design trick that makes it work is that the game gets faster as you win. Fewer invaders on screen means fewer sprites to draw and a quicker march, so every kill tightens the pressure rather than releasing it. The final invader in a wave moves at a speed that would have been unplayable at the start, and by then you have had two minutes to prepare for it.
Positioning matters more than aim. The formation travels sideways until it touches an edge and then drops a row, which means the columns you clear determine how far it can travel and how soon it descends. Clearing the outer columns first stretches out each pass. Clearing the centre first does the opposite and pulls the wall down on top of you.
It runs on a single canvas, needs no plugin and works with four keys, so a round fits into any spare couple of minutes. The source is compact and well organised, which is why it turns up regularly as a teaching example for game loops, collision handling and simple state machines.
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Common questions
Is this the arcade original?+
No. It is an independent open source rewrite by Dave Kerr, not affiliated with or endorsed by the rights holders of the original arcade game.
How do I start?+
Press Enter or Space at the title screen, then move with the arrow keys and fire with Space.
Why do the invaders speed up?+
Fewer invaders means a faster march. It is part of the original design and this version keeps it.
Does it work on a phone?+
It plays best with a keyboard, so a laptop or desktop is the better choice.
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