This game is like if Isolation and Fire Team Elite had a drunken one night stand that produced a kid that neither of them want anything to do with. It's like a Metal Gear game where you're given a massive arsenal but penalized for using it anywhere except boss battles or when the game explicitly tells you to fight. Basically somebody saw Aliens and rather than thinking what the Marines could be capable of, instead took the concept of 4 guys with a single magazine of ammo fighting a messy retrograde against an endless horde and assumed it was the only way the Marines could possibly operate.
Atmospherically it's so similar to the movie that it might as well just be taking place on LV-426 as Lethe is the same barren, rocky world that is in a perpetual night with light rain. Interiors are little better with even corporate offices looking straight out of Gateway Station. Even the repetitive comments from your troops are mostly quotes from the movie. The plot has all the usual facepalms that it needs to function and is basically the same plot from every Dark Horse Comic; it even forces you to make stupid decisions as the only way to advance the mission in some cases ('I know you're slaughtering these dudes but there's no possible way you can win unless you let the Aliens into the building with you.').
Both the combat and stealth are incredibly clunky as it's a real time game and your team simply moves as a single entity rather than allowing you to position them individually. This becomes frustrating as various abilities that require line of sight such as grenade launchers or sniper shots cause you to frequently have to expose your entire team just to get an angle to use the ability. When you faced armed human opponents this also becomes a liability as it's a crapshoot if there's a position with both cover and clear firing lines for all your troops; which is your only practical option as your troops move too slowly (even with speed upgrades) to effectively flood a room.
Both exploration and combat lean heavily on various expendable resources you either bring with you or find along the way. Command Points are a capped and slowly regenerating resource that are used for various attacks (grenades, flares, shotgun blasts, sniper shots, suppressive fire) and stationary motion trackers. Ammo is an uncapped catch-all resource for spare magazines, sentry gun reloads, and demolition charges for destroying certain walls or barricades. Medkits are capped and serve both a health and stress recovery function. Tools (also capped) are used to hack doors, repair sentry guns, repair synthetics, and seal doors. More often that not, these resources are behind doors you need to hack, tucked in out the way places, or in full on old school Doom style schmuck bait spots where getting them is impossible without alerting enemies.
Much of the gameplay loop revolves around a poorly implemented stealth mechanic where if you are spotted, it triggers an alert. Enemies, even human enemies, have a full 360 detection bubble that matches your own line of sight; so if an enemy is seen it's a race to either use a sniper shot on them or break line of sight. The sniper shot is your only direct fire tool to kill an enemy without triggering an alert and requires your scout to have a firing angle, swap to the sniper rifle, aim, and take the shot. This action consumes a Command Point and the detection meter is closing in through the whole process so it's impractical at anything more than long range if the enemy is moving in your direction. When you are spotted, it triggers an alert (Hunt) that dispatches enemies to your location at the time of the alert. The alert ticks down but pauses anytime you are spotted again. And every second the alert is going on, an enemy aggressiveness meter is ticking upwards towards increasing enemy numbers, introducing more difficult types of enemies, and making their patrolling more proactive; there is no way to reduce the aggressiveness meter other than leaving the mission and coming back later. This largely makes you look forward to fighting human enemies as the they don't effect the xenos alert and aggressiveness mechanics, so you can engage them at will.
Another big portion of the loop is stress management. Every second you are in an alert or fighting, a three tiered stress system ticks up with the second and third levels applying various debuffs such as accuracy penalties, increased ammo usage, reduction in Command Point cap, or causing the stress meter to tick up even when you're undetected. This is only reduced through using a medkit or using tools to seal yourselves in a designated safe room, which reduces stress when you 'rest', like a Resident Evil style save room. The stress gain happens no matter the circumstances, making it a weird case where your guys feel safer locked in a supply closet with aliens all around rather than rolling along in an APC laying waste to all comers.
The overall level design tends to actively teach you to effectively use a tactic then strip away its effectiveness. Long, unbroken sight lines rapidly turn to a CQC nightmare to make the sniper shot useless. Single entry point rooms or long, open hallways with dead ends rapidly switch to short areas with multiple entry points and tall clutter, severely hampering the usefulness of sentry guns. Maps with multiple good parking spots for your APC rapidly swap to lackluster positions if they are present at all. Maps littered with clutter that counts as cover transitions to almost nothing counting as cover when you're having to attack through heavy armed resistance. One section towards the end even completely removes the motion tracker as a gameplay mechanic.
The strategic layer is not without its own series of weird design choices. Nearly every aspect of upgrading your Marines is completely at the whims of RNG; from the binary choice of a class on reaching level three (where it's obvious the game demands that you unlock classes in a specific order and maintain an equal balance of all classes) to the completely random selection of three possible level up perks that always seems to be reluctant to dole out too many of the really good ones. Every single one of your Marines start out with a negative personality trait that range from manageable ones like a reduction in experience to game destroying ones like raising the whole team's stress even when undetected; and these negative traits can only be removed through a level up perk that seems to rarely be offered. After coming back from a mission your troops have a 'tired' debuff for a day, every health bar lost (even if healed) is a day of medical recovery needed, and each stress level they reached is a day of psychiatric counseling needed to avoid additional debuffs. There are also materials and xeno-samples you can pick up during missions; the former are used for individual troop gear perks and team weapon unlocks, the latter are used to research and employ various global buffs. The weapons seem nice in theory but with how CQC focused the game is, replacing the default shotgun with a flamethrower or RPG feels unwise, and even upgrading to a 'heavy pulse rifle' removes the grenade launcher ability in favor of minor boost to some weapon stats. The research projects range from great ones like those that reduce alert time and aggressiveness progression to some that seem too situational to bother wasting samples to use them in a mission.
In the end we're left with a game with a severe identity crisis that tries to be a lot of things but fails at them all. Most of the almost three hours it takes to clear a mission isn't spent in excitement or tension, it's spent in boredom as you stare at map, watching the grid of motion trackers you placed and waiting for a gap in the patrols so you can head for the next cluster of rooms.
