Preface: Found UFOai and installed it from debian repository. XCOM:Tftd is one of my favourite games, and I wanted to check UFOai out.
First impression: 3D models and modern graphics. Units appear plastic and the overall mood seems off. The essential gameplay mechanics seem to be the same as in the older versions, but some of them are lacking or malfunctional. UI seems a bit tasteless, screenshots from developer version though looked very promising. Somehow this game seems to be lacking all of that darkness and suspense you could find in TFTD, which engaged your intuition. Apocalypse version though had similar problems with look and feel, which hurt that game quite a lot. After getting used to the interface and getting over the negative first impression, the game started to seem interesting. I think the mood of the game is quite terrible it's like one of the primary problems I have with it, hopefully the developer version has improved in other areas in addition to the interface appearance.
Later experiences: After getting hooked into the game and spending way more time with it than what is healthy, some ironman/maxdifficulty attempts later, I came to realize that a large fraction of the comments I made in the post were unwarranted or already had a solution in options, but many of them seem very valid. I got used to the graphics and even started liking some of them. I think there are lots of good things in the game, even though my initial first impression was very negative. I do think that in many ways the gameplay mechanics are of a lower grade than in TFTD, but the are some additional features and additional content which make up for that, somewhat. Then, it was a commercial project, with funding and hired people to work, like professional artists lead by someone with design responsibilities. The algorithms maybe were older, the computer slower, but certain things still count under and on the surface.
I noticed that there are few people on irc, not a lot of posts on the forums, and the 'last' and 'monthly' development update news was sometime in 2018. It seems the project has stagnated (Game seems complete, too). Had I realized that the project is not going on strong, I would've probably abstained from making critical points, but I only realized that after writing the initial post. I'll list specific points below.
Geoscape & campaign
Geoscape polygons: They're big, and kind of tacky. I find them tasteless and too big. I think if you'd replace them with some minimalistic and tasteful symbol it would be better.
Seeing what the UFOs are immediately seems off.
Aerial engagement system: There doesn't seem to be a system and it's hard to make sense out of the engagements. The engagement system in TFTD was actually pretty good in comparison to this.
Geoscape panel is unpolished: It has this giant symbol that explains the navigation and on this version it has the same kind of ugly interface and it's lacking buttons.
Instant purchases: A conveniency, when you realize you've forgotten something and aliens show up, but it also hurts the mood. Besides some of the things still do take time.
UFOpaedia tutorial contents and categorization The UFOpaedia contents seem to be written like as a tutorial for the player and the information stored with in it, is arranged in that way. It's kind of offputting.
Government favour system? This was lacking from the xcom series too. Apocalypse tried to create a simulated ecosystem. Government happiness gives off a feeling that it's lacking a background logic. Did the aliens infiltrate the governments? Political resistance developed? Improvements here could be fun. Maybe you can't be friends with everyone? Some in-detail contacts with other organizations?
Purchases linked to specific nations? You could link the purchase system with specific governments, bad/good standing unlocking/blocking access to groups of products. E.g. aliens infiltrate a certain country and you lose some business transactions. (Replay value might increase with variable starting relationships & available items).
Ordering multiple items Now this is a very tiny feature, but for an example ordering 50 units of each grenade type at the beginning of the game is sort of tedious clicking. But it's not really an issue.
UFO Flight patterns UFO flight patterns and behavior are perhaps too simple. It's possible to lure UFOs within base defense range exploiting this. (E.g. Transporter out, gunboat attacks, repeat, or idle/retreat).
Prebuilt base I think it's too prebuilt. It's fun to try out different of starting configurations, though additional freedom may allow offstep from the intended rate of progression.
Off-duty training of units? A facility where you could have units improve some skills with time, if they're not wounded.
UFO Yard & UFO dismantling This system seems pretty interesting.
Is the production cost for items equivalent to the purchase cost in workshop? It might be nice if you could produce at least some items cost-effectively.
Flight path prediction and failure to intercept with short range craft armament If a craft is faster than a UFO, it flies ahead of the UFO due to path prediction. (E.g. Saracen equipped with shivas fails to intercept. Manual control avoids the problem, benign).
Geoscape aircraft menu? A new menu button to list and select any aircraft from the geoscape?
Powergeneration and consumption? Maybe powerplants could generate power and different facilities would have varying rates of consumption? (Compare laser, radar, storage).
Available recruits disappearing from list? Instead of remaining as an available recruits indefinitely, units would disappear from the list.
Variable quality of available recruits Perhaps being in good standings with specific nations would result to chance at recruiting improved units?
New facilities and related abstractions? New facilities for the management fun, finding intermediate abstract products (storage, power, manufacture, materials, communications..)
Towing downed UFOs and transfer crafts? Instead of UFOs appearing in the yard, a lifter craft to tow them? Transfers on actual airships which would risk being attacked?
Moodbreakers?
"Tactical modern firearms combat". Less "SWAT", more "X-Files"? A lot of the mood set by aesthetics, names and also the storyline content, implied background logic, including the name 'phalanx', seem to create this atmosphere of tactical combat based on modern firearms. This is a game with UFOs and aliens and alien species (also), and I think it would be good to try and shift the theme.
The standard interface is unpolished The interface looks a bit clunky. There's a green/gray contrast color theme going on, which was 'trendy' around the time UFOai was developed, but the choice of tones also seems unrefined.
Weird map details Some maps and map details simply come off as weird. (Fun: What I think are Svalbard Global Seed Vault remains appear on antarctic?)
Not having shroud, i.e. being omniscient about terrain kind of kills the mood too: I suppose this is due to the 3D mechanics.
Vision system Vision and detection system seems to be lacking. Worrying about what lurks in the shadows and getting ambushed is part of the suspense I was expecting, which didn't happen.
(Note: This involves that I've disabled shaders, as they don't seem to function correctly on my hw)
Alien and item models Taman wearing red T-shirts? "Generic" early guns. The list of aliens seems uncreative and lacking.
Upgraded bloodspider and upgraded hovernet seem redundant and repetive This is probably because someone has to make an animate models, and it's easier to take a pre-existing model and tinker with it a bit, than to create something new, so it's understandable. I think it would be nice if people got creative and came up with something fresh to replace at least one of those "new" hostiles, with something different.
Geoscape/Tactics
8 units per craft is very challenging: This is mostly an artifact of that I don't save the game and that I chose the highest difficulty (which many of you probably have tried?), but often times 8 units is not tactically sufficient. Especially because you end up losing some units anyway and although it sounds gruesome, but it's a game, so you might want to keep some units more than others, but with only 8 units on the mission everyone tends to get involved. Later you get at least 12 units per mission with the Herakles (I've not progressed further yet?), but it might be better if you started off with 10 and got 16 later.
Maps and missions incomplete pairings: Some map:mission pairings are not sensible. I'm assuming everyone is aware of this. a craft gets downed somewhere in the wilderness, you'd think you wouldn't run into civilians etc and that the mission environment would match that. But of course someone has to make those maps which is a lot of work, and then pairing them properly also requires that there's a system in place for generating the mission details based on geoscape location. I think the latter is present, but maybe flawed.
Maps are tactically kind of inconsistent I think it's good that there is variation between maps, but the requirements of particular missions can change a lot, and combined with the mission-map pairing system, this sometimes introduces difficulties.
There should be a way to arrange the order of the units on the transporter: So you could move units up and down the list, and that should affect the order in which the units spawn on the craft, so you have certain units exiting the craft first, and others later etc.
Craft inventory An (incomplete) craft inventory system was present in TFTD, and an improved version would be nice for UFOai.
Storage inventory? Perhaps the items in the storages could show up on the battlescape, and could be lost during basedefense?
Crews of downed and landed crafts? Alien crews could sustain injuries in the process of crashing or being hit?
Battlescape
Camera controls feel uncomfortable: This was my first impression, but I got over it after a couple of hours. Unit selection is erratic when clicking something on a lower level. If camera coordinates are outside horizontal bounds of the map, selection doesn't work properly.
Launchers and lobbing, arcs Maybe the way the arc is generated could be worked on. (Roll option makes up)
The enemies seen icon could explain how many the selected unit sees
Missions where units start outside craft: The automatically placed units get in wrong places, which could be improved on by simply having the units start inside the ship every time.
No vision, detection probability, nor lighting based detection system: Seeing this game with 3D models, but lacking such essential gameplay mechanics, makes me appreciate the old game a bit more.
Alien behavior seems odd For an example in base defense missions some aliens wander outside going to the edge of the mission area, facing the end of the zone, not particularly doing anything.
Some hostile units appear to behave as if they're aware of the location of units which they can't see Not knowing how it works under the hood, I suspect at least some if not all of the units have this. This creates certain issues, such as, the enemy units choosing to seek engagement in some circumstances, and avoid it in others. Being aware of this can help countering and/or exploiting the pattern.
First aid? It might be nice if the units could perform limited first aid on themselves. Units could have a first aid skill, some units might specialize. (Notably TFTD had a nicer unconscious/wound/firstaid system).
Encumbrance The problem is that encumbrance lowers time units, instead of (mainly) increasing TU costs for movement. Easily fixed by lowering effect on total TUs and instead increasing movement costs. (Note: Costs are low integers, which might cause issues and require scaling TU cost baseline).
Line of fire - Line of sight If a unit sees a hostile they should have LoF (With exceptions). Probably an artifact of the vision/detection system not working/existing properly. Partially because LoF check starts at center of model, while it should be higher (jawline?), also ignores crouch/stand. Partially because no aim location option (high/low).
Maps of variable elevation perform poorly 3D maps with lot of variation in elevation have a lot of issues with line of fire / line of sight equivalency and the layered clipping model/stratification. Maps with straight surfaces and right angles perform best.
Reactionfire is unrealistic and deterministic I'd prefer a random component to interrupts. TU cost of turning could be a thing here too.
(Also think: Alertness, partial vision, noticing something, reacting and intuiting how to act, and performing the action.)
Smoke too reliable There should be limited visual cover from a small amount of smoke. It's too effective and too exploitable.
Smoke dispersion and thickness Gradual dispersion and disappearance of smoke, different levels of visibility. Probably requires a vision/detection system.
LoS doesn't affect CTH Which is unrealistic and exploitable. (Smoke, garden 'walls') (Exceptions like partial LoS could exist).
Hit probabilities & number of shots & TU relationships This I guess is a question of taste and wanted level of realism. My preference would be lower than current TU cost for automated firing, with lower accuracy. This is not a system level issue, as it's a question of parameters in some configuration files.
Unit conditions and status enhancing effects?
Most games have some variant of effects which modify how a unit or a character functions. UFOai could improve in this regard.
Flammability? Incendiary ammunition creates a patch of fire, which then goes away after a set amount of time. It would be more interesting if some tiles were flammable and burned for a while, and other tiles wouldn't, things would catch fire and it would spread. Levels of intensity?
Stamina/endurance? Think this part is self-explanatory.
Aiming / Using optics for aiming? Separate aim step? Using a scope would produce a narrow LoS.
Bugs?
Odd behavior triggered by alien in a base without containment The "Odd behaviour" research item gets triggered by an alien captured into a base without alien containment. When you start researching, the item disappears due to missing prerequisites. I suspect it doesn't trigger again.