Spectrum Invaders – Relive the Classic ZX Spectrum Shoot ’Em Up

If you grew up with the ZX Spectrum, you know the thrill of fast-paced arcade shooters. Spectrum Invaders is one of those must-play retro classics, putting you in command as Earth faces a relentless alien onslaught.

Two types of invaders are hurtling toward the planet, and your mission is simple—but terrifying: stop every single one before they reach the deadly “X” mark on the left side of the screen. Let just one slip through, and it’s game over for humanity.

Armed with your trusty missiles, every successful hit brings you closer to saving the world. The action ramps up fast as the aliens advance, matched by the iconic two-tone throbbing soundtrack that keeps your pulse racing. Play on a colour TV, and you’ll see the invaders flash in red and yellow, adding to the excitement of this arcade-inspired shooter.

For fans of retro gaming nostalgia, Spectrum Invaders captures the essence of early ’80s arcade thrills on the humble ZX Spectrum. It’s a must-play for collectors, enthusiasts, and anyone reliving the golden age of 8-bit gaming.

How to Play Spectrum Invaders

Moving your missile launcher is easy: use the 5 and 8 keys (marked with arrows) to slide left and right. Press the 7 key (up arrow) to fire. Points are awarded for every alien you hit—the further away the ship, the higher your score.

The game ends when either:

• You’ve destroyed all invaders (Earth is safe!)

• Or one of the remaining aliens crosses the X mark (game over).

The staggered formation of advancing ships and the speeding-up action make every session tense and addictive, keeping you glued to the joystick.

Typing Tips for Spectrum Coders

Many classic ZX Spectrum games hide clever tricks in their code. Here’s what to know if you’re typing in Spectrum Invaders:

• Graphics Characters: The program defines four graphics characters at the start. The “+0” in lines 10, 100, 200, and 300 is purely cosmetic—helping the listing display characters clearly.

• Graphics Mode: Later, graphics characters appear in square brackets, indicating they should be entered in graphics mode.

• Variables: The variable “xl” is written as “xL” in the listing for clarity.

• Alien Rows: Lines 500 and 510 include spaces to stagger the alien rows, creating that iconic marching effect.

• Special Characters: Lines 1440, 1555, 1595, and 1635 use a full stop in quotes. Line 7020 ends with “TO)”—this is correct and matches the string slicing used in the final line.

These quirks are all part of the fun of Spectrum coding and add to the charm of classic type-in games.

Pro Tips for Mastering Spectrum Invaders

Want to survive longer and rack up high scores? Try these strategies:

• Target the back row first – high-value aliens are furthest away.

• Keep moving – slide left and right to dodge and line up shots.

• Time your missiles – fire one at a time for maximum efficiency.

• Use staggered rows to your advantage – gaps let you hit multiple targets.

• Stay calm when the game speeds up – follow the alien rhythm, don’t panic.

• Practice makes perfect – patterns become easier to anticipate with each play.

With patience and quick reflexes, you’ll climb the high-score table and hold back the invasion like a true retro gaming hero.

Subroutine structure

10 Define first alien ship graphics character
100 Define missile launcher graphics character
200 Define second alien ship graphics character
300 Define explosion graphics character
400 Initialise variable and set background paper and ink colours
500 Initialise strings
1000 Print aliens
1100 Print and move missile launcher
1400 Shoot missile
1500 Test whether alien hit and for end of game
7000 Remove aliens when hit
7510 Increment score when alien hit
7900 Print explosion, produce its sound and display new score
8000 Main play loop
8500 Losing message
9000 Winning message and offer of new game
9500 String function

Programming details

The alien ships are stored in strings and when they are hit a string slicing routine (line 7000) is used to replace the graphics characters by blanks.

Scope for improvement

You might like to add a routine to make the aliens shoot back at random so that the missile launcher faced the added problem of dodging enemy fire.

Program

Okay, Speccy fans—time to get coding! Let’s jump into the type-in program and see those invaders come alive on your Spectrum…

Saving Your Game to Cassette

In the ’80s, saving a ZX Spectrum game wasn’t just practical—it was part of the ritual. That screeching cassette sound was music to any Speccy fan’s ears. Here’s how to do it the authentic way:

You’ll need:

• ZX Spectrum

• Cassette recorder

• Blank tape (C60 or C90)

• 3.5mm MIC/EAR leads

Step 1: Connect the Spectrum’s EAR and MIC sockets to the recorder. Optional: use the REMOTE socket for auto-control.

Step 2: Insert a blank tape and rewind. Many gamers labelled tapes with names like Invaders 1983—building their personal libraries.

Step 3: On the Spectrum, type:

Press Enter. Then press Record + Play on the tape recorder and hit any key on the Spectrum.

Step 4: Wait for OK on the screen—your game is saved!

Step 5: Test by typing:

Press Play on the tape recorder. If everything works, your game will load perfectly.

💡 Nostalgia tip: Adjust the recorder’s volume to about three-quarters for best results. Old tapes and cheap decks could be temperamental—part of the classic Spectrum experience!

Relive the ZX Spectrum Magic with Speccy Shack

Typing, firing, dodging, and loading from tape—that’s the charm of ZX Spectrum gaming. At Speccy Shack, we bring that nostalgia to life.

Explore our collection of refurbished joysticks, classic ZX Spectrum games, and retro accessories to relive the excitement of the ’80s. Rediscover your favourite games, or share the thrill with a new generation of retro gamers.

Dive back into the world of Spectrum gaming—your next adventure is just a keypress away!