Hello all, Dartling Gun may or may not be released in Bloons TD 6 soon, but here are my upgrade paths/ideas (on medium):
Base Price: $800
Path 1:
Focused Firing - Decreases the spread of the dartling gun. $200
Faster Barrel Spin - Shoots much faster. $1200
Double Darts - Shoots 2 darts at a time! $2200
Dartism - Nearby darts receive +1 damage and +2 pierce. $4500
Bubonic Overdrive - Shoots extremely fast, and shoots 5 darts at a time! $20000
Path 2:
Powerful Darts - Darts move faster and pop 4 bloons at once. $650
Heavy Darts - Darts do extra damage to ceramic and fortified bloons. $800
Laser Cannon - Shoots out lasers which can pop 14 bloons, and can pop frozen bloons! (Cannot pop purple bloons.) $5500
Ray of Doom - A persistent beam of solid bloon destruction. $35000 (I really think this needs a price buff from BTD 5.)
Sunbeam Ray - Converts sunlight into pure energy which does massive damage, covers more area, and creates explosions upon contact. $65000
Path 3:
Posionous Darts - Posion darts do gradual damage to bloons. (Only affects 2 layers.) $500
Depleted Bloontonium - Darts can hurt any bloon type. $1100
Hydra Rocket Pods - Shoots out missiles with sharp tips that pop black bloons. $6000
Bloon Area Denial System - Shoots triple the missles. Ability: Shoots out 100 powerful missiles towards the nearest 100 bloons on the screen. $18000
Bloonsxtermination - Shoots out 200 missiles, does 2 damage, and has much bigger missile explosions.
Those are my ideas, I hope you like it. :)