I have fully upgraded the tech tree of this game and finished every mission of it. I think the game looks pretty, but many contents remain to be added. For now, the replay value of the game is poor. What's more, as hero is the only item which most players will spend real money on, I'm not sure the income from iron marines and the joy it brings to players can scale with the huge efforts of the developers. Here are my personal experience and suggestions.
First the game need an encyclopedia and a hint book just like those of kingdom rush series. It will also be good if player can have mutiple profiles.
There should be some way to deal with excessive tech point. Although it takes a lot of tech point to fully upgrade the tech tree, unlike the stars in kingdom rush series, this game have a unlimited supply of tech points. Maybe its a good idea to allow the players to enchange them for credits.
The Chinese translation is problumatic. For example one of the hints (which appears in the loading screen) is about "archers", and it should be replaced by "ranged units". I guess the original text is "ranger", as it may refer to either ranged units or archers. Maybe it is a good idea to ask some Chinese players for help.
There could be an alternative control mode, which allow players tap screen to select unit and tap elsewhere to move. Player also should be allowed to select mutiple targets by pressing the screen without moving, in which case an expanding circle appears and select every unit inside it when the user stop pressing. There can also the some tags on the top or right side of the screen, each of them represents a unit. Tapping one tag means select a unit, tap again to deselect, double tap to move to this unit.
Skimish mode could be very wellcome, in which the player and AI enemy players all start with a base at the corners of the map. The enemy players will try to capture new mines like the player does, and there should be different levels of enemy players, maps, objectives, starting units, time limits or rush timer, tech upgrade limits and special conditions for the players to choose from. Some maps can be free and some can come for a price. This is a good substitute of the survival mode of kingdom rush series, as suivival mode is unrealistic in iron marines due to the limited number of turrent slots.
Players also should be allowed to create a single save file in battle, which is deleted once current mission is completed and reward is claimed. This may prevent claiming mission reward for mutiple times, and no bugs will be caused by loading an old save file with upgraded tech.
If turrents can be built anywhere and more types of them are introduced, there can be much better defence missions. It would be even better if turrents, recruit pads and other support sturctures can be built around base, other turrents and engineers. It is true that iron marines is meant to be a simple RTS game, but its turrent system seems a bit too simple, so it brings few choices and fun.
The cool down of dorp cannon and hero revival can be increased, and there should be an option to complete the cool down immedietly with a small amount of resourse. This cost can be higher for stronger heros.
The balance of the game needs a lot of adjustions. Missles do very little damage to land units, the missiles of the missile turrents should do massive damage according to their visual effect, but in fact they need many shots to kill some of the weakest enermy. This is also true for the shellstorm, it is supposed to be good at dealing with large groups of enermy, but in fact it need more then 10 seconds to kill a basic acid spitting worm, and the AOE radius is also very small.
The turrents are too weak, as it takes 500-1000 resourses to maxiumize the defences of a base, but such defenses still cannot withstand a large scale attack. I guess it is way more cheaper and effective to use unupgraded turrent as meat shield and recruit snipers from troop pad for help, and the only thing prevents this is the population cap. Turrents can't move or transform, and this makes them unable to adjust themselves to deal with different enemy. Turrent skills, especially those of missle turrent, are extremely useless, as they are very expensive and receive benefit from no tech upgrade at all. In addition, the flame missile of the missile turrent sets the ground on fire, but the flame do no damge to those enemy that walks upon it.There needs to be some tech upgrades which greatly increases the damage and range of turrents, as well as those which further improves rader, shield and turrent skill. Currently,with the tech tree fully upgraded, the gun turrent doesn't do as much damage as rifle squad. The drop cannon is also a bit too weak in the late game and need further tech upgrades. It is supposed to defend the base in case of emergency or assault the enermy from behind at the begining of the battle, but without health upgrade it is unable to do these things. After all, all units can receive benifit from a large number of tech upgrades, but base defences and drop cannon only enjoy a few.
Snipers are way too powerful due to the amour pirecing upgrade. They can do massive damage to all units, no matter they are land units or flyers, light or heavy. The armour pirecing tech should allow snipers to deal damage with reduced armour, instead of ignoring armour. Their chance to instantly kill strong enemys also should be reduced.There is a special mission in which player should defend a communication center with 5 infentry squard and 2 mecha, and the only thing the player need to do to finish this mission is to transform all infentry into snipers and place them behind the turents. Few enemy can suivive until they attack if the snipers are well placed and upgraded. I fully upgraded all teches in one day by playing this mission again and again like this.
Mechas are diffcult to use in comparison to infentry and alien squad. If the tech tree is fully upgraded and difficulty is casual, it is easy to transform alien squard to light saber squad and use them fight all the way to the machine eye. Enemy drones are completely helpless against them. However if the player try to do the same thing with the mecha, then the melee mecha will make it, but take much longer time and lose more health. The flame walker is even less effective, and it can be destroyed if not controlled properly. The shellstorm's missles do little damage to the drones, but it can still make it with its powerful skills. The mecha squad looks much less efficient then the light sabar aliens, this is partly because drones' laser ignores their armor and maybe the light saber squad is a bit too powerful, but the primary weapon of mechas are also too ineffective.
The shellstorm is supposed to be a powerful artillary unit, but its range is far shorter then snipers, and its missles is useless anainst all land units except those can be easily wiped out by rifile infentry squad. Its defence robots are also too fragile, although their damage is a bit too high. On the other hand its waste granade is rediculously powerful, which kills weak enemies instantly and kills powerful enemies in seconds. It would be better if shellstrom have much more poweful missiles, and its waste granade slows and weakens enermy in a large radius rather then kills any enermy in a small radius. The flame walker have a range shorter then rifile squard and acid spitting worms, and they are also slow and not very tough. This makes them really difficult to use. Their flamethrower needs more then 10 seconds to destroy those basic medium battle robot, this could result from the bug which prevent the burning ground from dealing damaging the enemy. As a unit which is expensive, slow and weak against air targets, flame walker should be stronger to be useful. The melee mecha is even worse, as it is a very slow melee unit which do not automaticly move towards enemy until they are very close. In battle, it spend a lot of time walking between enemy rather then attacking, especially when backed up by ranged units. Additionally, the melee walker's fist is not that powerful in comparison to sniper suard and lightsabar alien squard, and its defence drone expires quickly and the mecha must stop moving, attacking or mining to rebuild them. This interupt mining and attacking automatically, thus greatly reduces their mining efficiency and damage output. The damage output of melee walker, its speed and the life span of its defence drone should be improved. Its AI should be more aggeressive, so that at least it can go forward and serve as a meat shield. Maybe its fist should be able to stun the enermy or do AOE damage(some says it do have AOE domage but it actually don't), as it have much less chance to attack and more difficult to disengage then the light sabar squad.
There can also be some further improvements, if they are pratical. For example, new tech upgrades which provides additional bonous and skills to units can be added, and player should choose to activate some of them between battle. For example there can be upgrades which allow the melee mecha to reflect melee damage, heal itself in battle, charge towards enemy and stun those who stand on his path, have increased speed and damage when attacked by mutiple enermy, have main weapon replaced by a earthquake generator, or hit enemy from a distance by launching its fist with rocket installed on it. There may also be other upgrades for the flame walker, such as cause its flame to slow enemy, improve its armour, cause it to explode on death, cause its range and damage to increase when not moving, or replace its main weapon with long range fireball launcher. There could be a hanger page next to tech page or hero page, where player can edit which upgrades to equip. This will encourage players to try diffrent combination when replaying diffrent games.
At last, new units will also be welcome, and they can also bring more in-game purchases. New units can include a mobile fortress which cost 120 or more resourse. It serve as a tank armed with laser, cannon or gatling cannon when moving. When not moving, it can expand into an area shield generator with laser, a heavy artilary plantform or a drone base with gatling cannon.
There can also be unit skins (which represent marines from different planets) which give no bonous or slight bonous to different units. They may come both for free or for a price, just like heros. I also would like to see special units which can only be built in certain missions, just like those special towers in kingdom rush. So does special units or special turrents which replace or serve as the second drop cannon or hero. For example, there can be a second drop cannon option which drops a flamethrower which can hide underground when there's no target in range, or a fragile rocket launcher which provides temporary fire support.