Castle Defender


The hordes are coming!

Wave after wave of goblins, skeletons, zombies, snakes, wizards and all manner of creatures from the nether dimensions are attacking our castle. It is up to you to save us from the onslaught using our defensive towers! Enemies will emerge from the portal and move along the path to our castle. Place different tower types that automatically attack anything that gets within their range.


Castle Defender is a tower defense game originally written for BBC Micro. I get in contact with the original author and used his sources to port the game to Atari XL/XE computers. You can read the conversion story HERE.

Castle Defender took 2nd place at ABBUC SWC 2019 and 3rd place at Kaz Compo 2019.

Current version is v1.3 from 2021.

Gameplay video


  • WASD keys or arrow keys or joystick move your cursor
  • Fire or Return shows build and upgrade options of selected tower or vacant space
  • Number keys 123 build a tower of that type in a vacant space
  • U upgrades an existing tower
  • Space or Fire speeds the game up whilst held
  • Start+Select+Option quit


Each tower has various attributes which are shown in the build bar accessible by Fire or Return.

LEVEL – Tower level (0-3)
DAMAGE – Amount of physical damage each shot inflicts
SHLD – Amount of shield damage each shot inflicts
RNG – Tower range
RATE – Rate of fire
COST – Cost of tower or upgrade

Build bar

When an empty space is selected build bar shows information for all available towers. If a tower is selected the current and upgrade values are shown.

Status columns

The left column shows your lives, gold and score. The right column shows the current health and shield ofthe enemy nearest the castle. * is the number of enemies left to destroy.


Each enemy has a starting strength and shield, values shown on bottom red enemy bar. If an enemy has a shield then any damage will be reduced by the shield amount. Destroying an enemy gives you a little gold but letting one reach the castle will cost you one life


Original BBC Micro code:
Original BBC Micro design:
Atari code and design:
Title screen:

Chris Bradburne
John Blythe
Martin Simecek
Piotr Radecki
Michal Radecki


Castle Defender
Castle Defender
Version: 1.3
49.2 KiB

Sources can be found here: Https://Sourceforge.Net/Projects/Castle-Defender/


Changes in v1.3 – 19.12.2021

  • added tower neighboring matrix based controls (more intuitive switching between towers)
  • added level unlocking (ability to start game from any level up to highest reached)
  • added game speed-up when fire is hold
  • fixed spawn point bug in Level 2 Wave 3
  • fixed glitches when quitting game right after starting a wave
  • added v1.3 indication

Changes in v1.2 – 09.11.2021

  • fixed splash screen glitching on NTSC
  • NTSC speed adjustments to match PAL
  • improved stereo playback
  • removed glitches in transitions between title screen and game
  • added next level jingle
  • added SELECT and START controls to the game menu
  • fixed sidebar stats set/reset when getting to the next level
  • fixed NTSC crash on Defeat (there was 50% chance to crash before reaching title screen)
  • fixed instruction scroll on NTSC – sometimes got stuck when holding SPACE
  • updated loading screen
  • added v1.2 indication to the game title

Changes in v1.1 – 09.02.2020

  • added game statistics on progress and enemies killed
  • added forgotten command to disable Basic ROM during loading
  • fixed PMG overlay data error when build bar is visible on phase change
  • fixed bullet leftovers on enemy path
  • fixed enemy hit-sprite leftovers on enemy path
  • added error sound when tower build or upgrade is not possible
  • fixed transition glitches between game screen and title screen
  • added v1.1 indication to the game title

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