Metal Slug X

I feel like if somewhere to say Justin, you're forced to bet what year did the first Metal Slug come out, I probably would have guessed 92, 93. Like 96 is like after the PS1. Especially since it was an arcade first game. It's this style of game in 96. Well, 3D, everyone was just so sort of enthralled with it. After a toy story came out, it was rare. Now they're turning it into a tactics series apparently. But I don't know how many actual like main Metal slug games there are. Are they? Everything is just like a bastardization and remake in port now or is there new stuff stuck?