Very nice!
I didn`t play the first version, but this one is really good to me as an oldschool fan. Especially the atmosphere is great.

Gameplay: You`ve got some really nice ideas here (I like finding keys and travaling through portals ), but you could make some more things here to get more variety. How about some ability stages, mysteries, script events, secret areas? The level design detail grade could be improved, too. So be creative and make some great things here.

Weapons: I`d like to have some more weapons a bit earlier in the game. I`m in the middle of the second level now (played about half an hour) and it was really challanging to me to make it through with just a hammer and a pistol with a constant "low on ammunition" (which was good). More variety would be nice. How about a rocketlauncher, an energy gun, grenades and other explosives? Of course you shouldn`t give it all to the player directly in the beginning, but in the beginning of level 2 (the space map) I`d love to have some more possibilities.

Oh, and an automatic saving system would be nice.

Overall: Good oldschool game, nice atmosphere, but you could still do many imporovements to make it great.