This is a bridge constructor game first and foremost with Portal elements and lore added on top of it. That is to say that while portals are central, the tunneling mechanic doesn't really add any depth to the game. Portals are pre-created; fixed in position by design, thus detracting from the creative process that makes the portal series so captivating. Some interesting rules still apply like conservation of momentum but, as said, portals feel more like a gimmick; something put there to rebrand a game outside of its genre.

This prefaced, it's still a quite enjoyable game. If you like similar games (disclaimer: I'm not really familiar with the genre), there may be something for you here. It's also technically very well done with nice graphic and optimized enough to run on fairly old devices. Be aware though that, depending on the platform you're using, you may be in for some frustration. As I played it on a mobile device, with a touchscreen input method, and as levels became more and more difficult and complicated, it became apparent how limiting and laborious it was to design the bridges as I wanted them to be. Not only it was quite hard to approximately place the pieces where desired without (and despite) constantly zooming in and out; on top of that the game seems to require a fruitlessly high level of precision in some levels with the undesired result of extinguishing creativity in favor of needlessly high engineering toil. Levels are not hard per se; solutions don't require a high degree of creativity and experimentation. Levels are hard because in some of them pieces need to be placed and adjusted multiple times so that the car might complete course while at the same time guaranteeing the orb bounces at the right angle. It's tedious work! Summarizing, play it with a mouse and keyboard or with a really big screen if you want to go the touchscreen way.

I should mention that there's also GlaDOS and the classic aperture science stick figures animation presenting stages and story progression. They are cute but don't expect them to add anything interesting to the story. GlaDOS is also a prototypical caricature of what you might be familiar with.

In conclusion, buy it if you like bridge builder games (though I'm not familiar enough with the genre to say whether this is a good representation of the genre or not). However I suggest against buying it if you're a portal fan and you just expect to find something interesting from that point of view.