Great rogue-lite with addictive progression system
While Risk of Rain may look like a simple horizontal shoot-em-up on the surface (my girlfriend remarked on seeing me play that it must be 20 years old), the different abilities and characters that you unlock while progressing through the somewhat randomly generated worlds really make you want to go back in time and again.
Every stage has the same basic goal: find the teleporter to the next stage and activate it. Time is of the essence however, since the game gets progressively harder every 5 minutes, determining the strength and amount of enemies. When you start on "Very Easy", enemies are easily dispatched and few and far between. Dawdle too long however, and huge beasts will spawn that take an inordinate amount of effort to kill. On the highest difficulties, even bosses will spawn, which are usually reserved for the moment when you activate the teleporter. A warning pops up on screen, and 90 seconds count down while you fight off a huge group of enemies. If you make it through, you'll have to mop up any stragglers before progressing through the beautifully detailed alien landscapes of Risk of Rain.
Each character class has 4 unique abilities, one of which is their basic attack. Rolling or backflipping as well as stealth will help you traverse the environment or evade enemies, but most skills are geared to unleashing as much carnage as possible among the alien creatures that randomly spawn around you. Rockets, Mines, Homing Missiles, even Glaives that bounce between enemies - you name it, Risk of Rain has it. Killing monsters and opening boxes along your path will earn you XP that will naturally level you up as well as money, which is required to open treasure chests or gamble on a variety of shrines - gambling is usually cheaper but has a chance of failing as well. Be aware that none of the items and levels carry over into the next match - the moment your character takes a dirt nap, it's back to square one. Typical for a roguelite: You unlock new characters and items along the way as well as learn about the intricacies and combinations of items that work best with your strategy.
Now the items are hugely varied, some simply increasing jumping height or regeneration while others completely change around what is possible. The Jetpack for instance will enable you to reach places your previously could not (and hover over the action, which for the mine-laying engineer class was practically indispensable to stay out of harms way) while another item will increase your hit points for every enemy killed. Get this early enough, and with the hundreds of enemies you will crush along the way, you'll be swimming in health. Very much like Diablo, the items you find are tiered - many of the more powerful gadgets won't spawn until you've satisfied certain requirements such as killing specific bosses or reached later stages.
This game oozes personality and mystery that few games manage to pull off these days. It is highly addictive and will keep you hooked for days. One of the best games of the past year for sure.
tldr: Don't spoil the game for yourself by reading reviews and guides. Buy it right now and experience it for yourself.
I may update once I get to try local multiplayer. It does seem to perform badly with 2 people onscreen, as well as lots of enemy sprites.