Some of SNK's pre-NeoGeo games are well-remembered, and much-loved, like Athena, or the Ikari Warriors series. Bermuda Triangle, by contrast, is neither remembered or liked. This is half an injustice, as though it definitely doesn't deserve to be liked, it should at least be remembered for being one of the most bizarrely-designed shooting games there is.
To start with, it uses a rotary joystick, which is only strange from our modern point of view, because no games have really used them since the late 80s, which is when this game was released, and when SNK had a minor fascination with the device, releasing (as far as I'm aware) more rotary joystick-controlled games than anyone else. But as I said, it's only a starting point, and though at first glance, Bermuda Triangle looks like a generic late 80s shooting game, it has a whole bunch of weird gimmicks thrown in.
So, your ship. The first thing you'll notice about it is that it's huge, big enough that avoiding enemies and their shots is a lot more difficult than it is enjoyable. Then, as you play, it'll keep changing form. This is because your health bar and the power of your weapons are linked: when you collect power ups, you gain health, and when you get hit, you lose power. When your ship gains or loses enough health to have its weapon power go up or down, it also changes form. Coupled with the fact that your ship is huge and will be getting hit a lot until you get used it, along with the fact that power ups appear seemingly at random, this all adds up into a baffling experience for the first-time player. With this, I can at least see what they were trying to do here: the idea of a form-changing ship is pretty cool, and the concept of weapon power and health being linked makes sense from a thematic standpoint, if not one of game balance. It's just the execution and a lack of explanation that really let the game down here.
Bermuda Triangle's other big weird mechanic is the way you play through the stages. First, you fly up the stage, like you would do in any other vertically-scrolling shooter. But then, you reach the top, and start going backwards, back down the stage, still fighting off enemies (using the rotary joystick, or whatever substitute you've configured for yourself in MAME to turn your ship's gun around). THEN, when you get back to the start, you fly up the stage a second time, with different enemy layouts than the first time, and at the end of this run, you fight the boss. It does this for every stage, and I really have no idea what the developers could have been thinking with this. Was it a way of trying to force players to change their firing direction? Was it just an attempt at making stages longer without having to draw more background graphics? Whatever the reason was, it falls on its face. It's annoying, it doesn't make any sense, it's a bad move all round.
I really can't recommend playing Bermuda Triangle, and I find it strange that it was released. It feels like some kind of experimental game that might have been made internally to try out a bunch of ideas the devs had, but it was actually released into arcades, though presumably, not many, and not for very long.