I thought this was only coming out next week, but apparently it's out right now! I've put 60 minutes into it, and so far it is fantastic. (I'm also cross posting this from elsewhere)
Briefly: it's Super Metroid meets Portal, with a whole lot of retro 2D charm and some ingenious puzzles. It's also only 240 points!
It's a Metroidvania, undoubtedly, but instead of acquiring new abilities you get new "gateway guns" - the first being one that produces two transportation gateways. Walk through one and pop through the other. Having only played an hour I've only gotten two guns so far, the second one shrinking or enlarging your character.
The puzzles for these are ingenious, taking into account not only location, but also gravity. If you can't jump horizontally far enough, you can put a gateway on the nearby wall, and the second one at the bottom of a shaft, and then jump down - the inertia you build up will fling you through the one on the wall, clearing the obstacle.
You can also acquire extra health pick-ups, a jump booster and a torch for dark areas (this is also needed for light-sensitive puzzles).
There's also enemies to negotiate, and so far they can be defeated like Mario enemies. Jump on their heads enough times to kill them. Some are particularly large, requiring you to increase your size before taking them on.
The best bit is the map and hint system. Instead of doors like in Metroid, it's puzzles which block your path. Every puzzle has a help point, where you can spend the power balls you've been collecting. Spend 5 and it tells you if you have the needed gear to solve it. This is fantastic, because at a glance you can check the map and see where new areas are available to you. Something which is frustrating in similar such games is not knowing when you're able to pass through earlier obstacles, but now you can just check the map and see, ah! I can now access that room from earlier.
If you spend 40 balls meanwhile, it shows you how to solve the puzzle. Which is great for people who get stuck. You can't really abuse it though, because out of the... I'd say 8 or 10 puzzles I've solved so far, I bought the solution for two and now I'm completely out of energy balls. So it's not possible to buy your way through - save them for when you need it.
My only criticism is that it's an Indie Game. Meaning you have to be online to play. But the game is also available for PCs, DRM free, if you prefer that route.
I can see this being something I put a lot more time into.