Serveral Suggestions

[LightningLord]

As you will see, I have tons of suggestions for Castle Defense:

Graphics

Not very much, just that the fonts should be more retro-sytle to suit the rest of the game.

Buildings/Towers

First, start with the Towers:

Ice Tower
Speed: 100
Range: 75
Damage: 0/50% Slow for 2 secs
Cost: 30
Health: 60

Hammer Tower
Speed: 25
Range: 150
Damage: 2
Cost: 75
Health: 120

Knocks back Creeps by 10 Range. On upgrades, it's treated as a Cannon Tower.

Ghost Arrow Tower
Speed: 300
Range: 100
Damage: 1
Cost: 30
Health: none

Creeps will walk through it. On upgrades, it's treated as an Arrow Tower.

Lightning Tower
Speed: 50
Range: 400
Damage: 4
Cost: 60
Health: 100

Damages all Creeps in a line.

Heat Tower
Speed: none
Range: 10
Damage: none
Cost: 25
Health: 150

All creeps in range gain 1 Damage each time a creep gains chance to attack.

Corruption Tower
Speed: 100
Range: 150
Damage: 1
Cost: 40
Health: 100

Lowers damage permanently by 30% when a creep is hit by this tower.

So, these were the towers, now the structures follow:

Detector
Cost: 50+20/Detector
Health: 20

Towers that are next to the detector gain +20 speed.

Food Box
Cost: 25
Health: 160

Creeps in 60 Range will be lured to the Food box.

Research Center
Cost: 100+100/Research Center
Health: 50

Reasearches cost 30 Gold less (But they will cost at least 50% of original).

Portal
Cost: 35
Health: 100

At end of Round, one of the following 8 things will happen:

-Your walls have +30 Health next round.

-Range Upgrade will be reasearched without gold cost.

-All your Towers do 1,5 times more damage next round.

-2 Oil towers will be places randomly on the map.

-There will be 10% more enemies next round.

-You lose up to 100 gold.

-Your walls have -40 Health next round.

-A building at random will be destroyed, and you gain 25% of its gold cost.

Mine
Cost: 2
Health: 1

Does 5 Damage to the creep that destroyed it.

Moat
Cost: 40
Health: none

Creeps can walk over it and lose 25% movement speed when doing so. Does not stack with any other form of slowing.

Upgrades

Since there are new buildings, there should be new upgrades for them.

Adds 0.2 Damage to Mines. 100 Gold, multiple upgrades

Crystallize the projectiles of Ice towers to let them cause splash damage. 300 Gold, single upgrade

Adds Uranium to Heat towers to give them +3 dps. 400 Gold, single upgrade

Strengthens Food Boxes to give them +40 Health. 350 Gold, single upgrade

Adds negative energy to Corruption towers for 15% additional damage reduction. 500 Gold, single upgrade (Note: The tower has 45% Damage reduction then.

And here are some generic Upgrades unrelated to the new buildings:

Gain 1 extra score per creep kill. 200 Gold, multiple upgrades

Regain 1 extra gold for selling. 150 Gold, multiple upgrades

Adds spikes to Walls so that they deal 1 Damage each time a creep attacks them. 400 Gold, single upgrade

Gives you 10000 Score with a chance of 4%. 400 Gold, multiple upgrades

Creeps

There should be some enhancements for creeps that occur with a chance of 10% for each enhancement. Here they are:

Kamikaze
Graphic: The Creep is pulsing
Effect: The creep has double speed, infinitive damage and dies on attack.

Camouflage
Graphic: You don't see him ^^
Effect: The creep does half damage, but can only be seen when he attacked once.

Heavy
Graphic: It is darker
Effect: It moves at half speed and has double health and damage.

Annoying
Graphic: It radiates yellow rings
Effect: It's twice as fast and all towers try attack it.

Swift
Graphic: They spin
Effect: Attacks on them miss at a chance of 10%.

Thats all for now, folks!

[Cyngus Unlimited]

Not bad, but there needs to be a few more enemies.

[LightningLord]

Maybe.

And if you have any suggestions of this kind or some balancing issues, post them.

[Cyngus Unlimited]

I got an idea for an enemy-

Super
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Graphic- Red and Blue disc
Effect- only appears once in every 10 waves, but has double speed, health, and damage.