I think you need to redesign the UI a little. As I said earlier, I think it's too many mouse clicks to do common/repetitive things. You should try to compress it more. There's slightly too little stuff on the different tabs, and too many tabs. xd I realize that this may be good for smaller screens, but as I have a 1920x1080 screen, the distance between buttons is huge. Generally makes it hard to micromanage, which the AI then will dominate you at.
I agree with more info in the tooltips. I also have no idea what the different race parameters did, so I just picked something. I think more information on the map would be good too. I thought it was hard to distinguish free star systems from the background, so a small frame or marker around them would be nice.
Finally: HOTKEYS x 10^99. Any hardcore RTS fan is gonna want them anyway. xD
I have fixed so that when accessing a star it will have the same menu open as the last star you clicked on. Went through hotkeys and shall see if I will fix that the next 7 days or so.
Tooltips will be extended slowly, will just have to figure out which tooltips which are to contain what info.
Will see if I can make the free stars more noticeable.

To scroll the map (I don't speak about the "minimap"), you use WS/AD which is really annoing since my A and W are not at the same place. So my first reflex, click and drag with the right button (so I have discovert how to explore Grin). Second try, click and drag with the left mouse button. Third try, click and drag with the middle mouse button.
Right now your scrolling is done square by square. A smooth scrolling is done pixel by pixel (or so), it will give a far better felling (a continuous space) but it may use more graphical power.
Will see if I can fix some kind of mouse movement. Probably won't be by pixel by pixel though as it would need a bit of a change in the engine.
An INGAME options (even if you have to restart the game)
Have considered it and think I will add something in that regards, sad problem is that I can't save the option for the future without an option file (which I try to avoid until further notice) so you need to tell the game to do it every time you start.
OK I give it a longer try... and loose in 1/4h
Nice that my AI works.

Build some defences (mine field,...), but I have NO IDEA if there where really build I didn't find anything about them on the star system info or fleet.
I know, that's my mistake. Planetary research is quite new and I haven't fixed it fully yet. That defense is to be hopefully shown in the info tab in the next version.
And regular army are placed OUTSIDE the squares, really strange
Actually the things you see to the right are the units which are contained within selected fleet.
Where did you think the units should've been shown?
What would be a more intuitive way to show that?
Then Aliens attacks me... and win the planet. NO DEFENCE !?! What the #@!*# ?
That's really strange?
As you lacked star ships I'd guess it may state that your star lacked a fleet defense, though as you had armies, didn't it say something in the line of:
"Defender killed 4 of 20 invading armies.
Invaders killed 5 of 5 defending armies"
And as you had planetary defenses it should said:
"Planetary defenses destroyed"
??
If it didn't I haven't been able to replicate your error and if you see it in the future, could you please make a screen shot there I can see the battle report?
At least, I got 5 other stars. So I wanted to do research about war... can't selected it. Ok research on spaceship then.
War tab is still in the works. Tabs that are red are currently not supposedly implemented (War and Planetary).
Use hull research until a future version is done as to use for war.
I have no clue how to deal with fleet, it is totaly unintuitive. I click everywhere hoping that something append... and I manage to send some ship to attack (I don't even know how many).
You send the fleet which is shown and you currently just send from one star to another star.
Will see if I can make the fleet handling more visual and easy to understand.
My ships arrived to the enemy star system and they WIN !!! Yahooo ! But they didn't invade the planet and they are coming back Shocked... it is a monarchy, i will execute them all
You need regular armies for the ground invasion. The star fleet can just break through the enemy space defenses and open up a siege of the planet, you still need groundies to do the heavy lifting.

There is some work to do at the UI level, a lot of thing is unintuitive or difficult to understand. Well it is not too much surprising for a first version of this kind of game. People react differently and developpers are to much in it to notice this sort of problem.
Yes, it's hard to both try to understand all users' problems with the game and at the same time try to make a easy solution that won't force the developer to change the engine. It's quite hard sometimes as I know I did some errors in my early engine decisions (as I wanted to develop a game quickly rather than allowing more visual designs).
Will see what I can do! Thanks for the information and testing!
