I discovered BD1 when it came out. I was about 6 or 7 and back then every game on the C64 seemed amazing (I especially remember Kotokoni Wilf).
I was very bad at BD gameplay and any level where fireflies could be let loose would be extremely scary. I was also slightly scared of killing them with boulders because I guess I was intimidated
I made a poster for BD, using a cutout of an advert for the game, screenshots, and my own writing, stuck to cardboard, and I gave a talk about it at primary school.
First I'll describe my thoughts on BDI:
This cave was easy enough, though I remember not being able to beat it on levels 4 or 5, which just seemed insane. The colour scheme here became burned into my brain and it's my favourite colour scheme to use with caves - it has a special nostalgic feeling which I try not to overuse.
This was also easy, and another favourite colour scheme (in particular I found the pink dirt appealing, lol), but I couldn't complete it on the higher levels because the roaming fireflies terrified me.
I had MUCH difficulty with this even on level one. Obviously I didn't have the logical thinking and planning that I have now! Colours give this a dark and foreboding feel which suits it.
When I was a few years older I could get here easily, but I didn't like killing the butterflies, it made me nervous. These days I gleefully waste those butterflies without a second thought, showing a marked increase in ruthlessness
Lots of trouble here. When I came back to rediscover BD via emulation, I developed a solution to this cave (going through the squares right to left) which made it infinitely easier. In the 80's I could get past this level but it caused a lot of sweating!
Not so difficult as previous cave, thanks to the boulders, so I managed to beat this cave on easy levels in the 80's fairly consistently.
I never got past this cave in the 80's, because I had no idea how to make more diamonds

By the 90's I was going to computer clubs and learned how to solve this level, but it was still quite difficult to do. The fact that the walls are green with the amoeba means that this colour scheme made a big impression on my imagination.
Never got here until early 90's.. Since I'd never seen these caves before it was quite exciting. Of course I'd used the C-Kit and played BDII before I saw this cave, so I was under the impression that all caves were in fact made in the PL-CK.
Classic cave, quite tough to beat but I could do it in the 80's. The masses of boulders and diamonds that you can't reach down the sides give it a mysterious air. The way the boulders and diamonds fell down and made piles seemed very realistic.
This level would always finish me off in the 80's. It wasn't until I was a lot older that I grasped an understanding of how to predict and manipulate the firefly's movement and trap them in loops. Once or twice I beat this screen in the 80's, by fluke, lol
A very devious cave on any level which I still find tricky to this day!
I remember feeling slightly disappointed by this cave when I met it in the early 90's (after a lot of struggle beating the prior few caves). I still didn't have a reliable concept of breaking walls with explosions, but I could do it - it was a bit hit and miss.
Classic cave with classic colours and of course the amoeba. I found it hard but I could beat it in the 80's, if I concentrated hard, lol
Never got past this screen, until I came back to the game in 2005. It was just too hard back then. I was however fascinated with the way this cave consists of a large amount of almost white dirt.
When I got here in 2005 I found it to be another disappointing screen. The space to the right isn't utilized at all and the magic wall gameplay is made awkward by the engine bug.
Also slightly disappointing and anticlimatic, but it is a good cave. Maybe a unique colour scheme would've made it more appealing. It can also be quite hard to get the right amount of diamonds but then it IS the last level. (The last level of BDII was much more satisfying).
Thoughts on BDII and the PL-CK:
We recieved BDII also when it came out, and upon playing BDII I found it not only a great sequel, but it gave me an almost spiritual yearning to have a construction kit. When my prayers were answered a little while later, I was in 8 bit heaven! I made many caves with this which are lost to the winds, most of which were utterly terrible as I still didn't have an overall sweeping vision spanning the entire gamut of BD gameplay, which I feel I do have today.
Modern times:
It was actually discovering the Crazy Light CK on the Internet which got me back into BD designing. Though ironically, while I initially wanted to build with this advanced kit, I've so far done most of my work using the original PL-CK, and want to continue in this vein, experimenting with all the possible effects and styles you can create with this early technology, before moving on to the much easier and luxurious CLCK.