I'm new to game development and I need some advice. I'm building a web based 2d random map generator and I wonder which algorithms there are to create such random terrains in a simple matrix as seen in the images below. It would be great if anyone could point me to some terms/algorithms as I have absolutely no clue what to search for.
Note: I'm not interested in depth/biomes - just the generation of those 2d shapes that grow from a starting point.
I tried implementing it in several ways - but all attempts seem rather childish and don't really produce the desired result. First I started with a small pattern like a plus (5 cells) and replicated it always on the edges of the already generated cells. Another way was to define cubes in different sizes and then start to generate big cubes in any direction, after that put medium cubes on some random edges, then again with smaller ones etc.
Any tips are very much appreciated!