![]() ![]() The algorithm that controls the main enemy attacks is a short but ingenious routine that Scott himself admits to not fully understanding (neither do I), but it results in varied and smooth attacks. I don't much Z80 but I was able to learn just enough to convert it to 6502 for the C64. The only way I could see to reproduce this authentically was to port the arcade code for enemy movements and timings directly.įortunately there is an excellent reverse-engineered disassembly of the Z80 arcade code by Scott Tunstall to work from. ![]() ![]() They have smooth sweeping movements that gradually change speed and direction, and are slightly different with each attack. It took just a couple of hours to getting it looking like Galaxian, but in playing the arcade version I realised the enemy movement is very different to Galaga. DevelopmentĪfter finishing Galaga I intended to work on Robotron 2064 and Funfair Inc, however a post on the C64 Facebook group about Galaxian got me thinking whether it would be easy to convert Galaga to play like its older brother and improve on the existing, jerky character-based Atarisoft port. Current record is 50.22 seconds by Eric Akeson. Attempt to clear the first stage in the fastest time possible.The last life can only be lost by the player who is losing at the time. You both work as a team to clear the level while competing for points. In two-player mode you play at the same time, sharing the three lives.When the swarm is almost clear they will switch to ultra-aggressive mode and continually attack with erratic movements and loop-the-loops.However an unaccompanied flagship will leave the stage and fill a gap in the top row on the next, meaning there could be up to four flagships at the start of a stage. Aliens that fly past you off the bottom of the screen (or abandon their attack off the side of the screen) will rejoin the swarm from the top.However depending on their angle of attack it might be wise to allow the flagship and convoy to pass and wait for a better opportunity. Taking out two escorts then the flagship will net 800 points, a large amount in a low-scoring and tricky game like Galaxian. To score maximum points from a flagship you must take out the red escort aliens first, and then the flagship.However, killing a flagship calms the swarm for a period, allowing you to pick them off in formation while they recover. As time passes and more enemies are killed, enemies attack in greater numbers and can drop more bombs. The yellow flagships are the key to both scoring large amounts of points, and to calming the swarm.However when they attack on their own their speed is faster than blue but slower than purple. Red enemies will generally attack alongside a flagship, mimicking the flagship's movements and protecting it.Purple enemies move the fastest and have wide, sweeping movements, allowing them to target you from the opposite side of the screen.Enemies from the middle row move slightly quicker. Blue enemies move the slowest and have less sweeping movements making them easily avoidable, but are nonetheless dangerous when attacking in groups or if you get trapped on one side of the screen.When a stage is completed the next stage will begin with a faster diving rate and higher number of simultaneous attacks/bombs than the last. As time goes on and the swarm is cleared, the enemies will dive at a faster rate and more will attack at once.Unlike Galaga, the swarm is able to sense incoming shots that they would otherwise move into and stop until they have passed. The swarm moves from side to side, shooting enemies in formation is the easiest way to clear enemies but also scores a lot less points than hitting a diving enemy.On web version above, left/right arrows to move, Z to fire. You can only fire one bullet at a time so make them count, if you miss you'll have to wait until the bullet leaves the top of the screen to fire again. The aim is to clear each swarm of aliens while maximising your score, dodging bombs and diving enemies in order to stay alive. ![]()
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