Record Player Movement to play back later

[Havie]

So, for my Space Invaders, I want to let the game play itself whilst in attract mode.

I guess that the easiest way to do this is to record keys used in a few seconds of play and then save this list. Then reload with the game and if in attract mode to use this list of commands to control the player?

My initial thought was to just dim demo(1000) and record left as 1, right as 2 and fire as 3. Each loop I store the key command in demo(number). Then in attract mode I just cycle through demo, read the number and use this to control the play as if the key has been pressed?

My issue is that I have no idea how to save the array demo and reload it. I know it is to do with openfile and savefile (I use this for saving and loading high scores) but don't understand what to do!

I was looking at the Tape command but I am unsure if this will work?

Any help would be much appreciated as currently I just used random numbers and player looks a little bonkers in attract mode!!!

Thanks.

[Daedalus]

Yep, that's a reasonable way of approaching it alright. Just make sure you don't run past 1000 frames or you'll have a crash on your hands

The simplest way to store it, though not the most efficient, is probably to just print out the values to a file and then read them back in in a similar way. The result will be a big text file with one number on each line, so you can easily edit it by hand afterwards if needs be.

Something like this should work to write the file:

If WriteFile(0, "Path:to/DemoFile")
  FileOutput 0
  For i = 0 to 1000
    NPrint demo(i)
  Next i
  DefaultOutput
  CloseFile 0
Else
  NPrint "Error writing to file!"
End If

And then to read it:

If ReadFile(0, "Path:to/DemoFile")
  FileInput 0
  For i = 0 to 1000
    If EOF(0) = False
      demo(i) = Edit(5)
    Else
      i = 1000
    End If
  Next i
  DefaultInput
  CloseFile 0
Else
  NPrint "Error reading from file!"
End If

[Havie]

Thanks - will have a go.

[Coagulus]

For a shorter file you could store pairs of numbers first one for control state (left, right or none) and second one for the number of frames for that state?

(Although then you'd need a second list for the frame time until fire is pressed then though too. But the file would still allow a long demo.)

[E-Penguin]

You could implement a simple AI to play the game, might be easier.

[Havie]

Originally Posted by E-Penguin

You could implement a simple AI to play the game, might be easier.

Not sure creating AI to play is easier than just recording me playing!

Easiest option is just a load of data statements to fill the dim as I already have it working randomly!

[E-Penguin]

AI doesn't have to play well... You can move in a random direction for a random number of frames, then repeat. Fire at random intervals.

Frankly that's how I play it anyway!

[Grumpa]

Some years ago I wrote a python version of space invaders. The attract modes I implemented as two lists one for each of the two demo games. I recorded the game in Mame and then counted frames and made a note of the state of the missile base, aliens and bombs and converted that into my lists. They are attached, you may or may not find them useful - I don't know Blitz basic, so the attached may be of no use at all!

[Havie]

Thanks - I will have a look, sounds really helpful!

[Havie]

Looking at Grumpa's code and linking this to Coagulus' idea I think I can probably use data statements and a dim but not have to have too long a list.

If I use the idea of storing a frame when something happens then I only need to store the key points and not all the bits in,between. For instance, if the base moves 20 pixels right then I just set which frame it starts moving right and it can keep moving until I set another frame that fires or moves left.

And Grumpa has provided all this info!

Cheers to all.