BTD6 is a remastered version of BTD5 and many others

BTD6 costs --

$4.99 (USD)
$7.99 (AUD)
$7.49 (NZD)
[On the app store]

$10.00 (USD)
$14.50 (AUD)
$12.39 (NZD)
[On steam]

There is 4 diffrent elements of monkeys/towers
Primary - the first element you unlock
Military - the second element you unlock
Magic - the third element you unlock
Support - the forth element you unlock

As you might now BTD6 has heros unlike the other games in fact as of this guild there are 8 types of heros! they will be list below

Quincy (Archer) - Proud strong and intelligent Quincy uses his bow to perform feats of amazing skill Quincys arrows bounce to up to 3 different targets

Gwendolin (Pyromaniac) - Gwendolin believes there hasnt yet been a Bloon problem that cant be solved with fire Lots of fire Blasts Bloons with fire from her pyro gun

Striker Jones (Artillery Commander) - Striker Jones is a strong Commander who uses his knowledge of long range combat to greatly boost the power of explosives Striker Jones shoots a powerful bazooka to explode the Bloons

Obyn Greenfoot (Forest Guardian) - Commanding powers of nature Obyn can shoot through solid obstacles with his spirit wolf attack Sends wolf spirits to attack the Bloons

Captain Churchill (Tank) - in his armored battle tank the Captain is a no-nonsense powerhouse on the battlefield Piercing bombs shot from the tank can explode up to 3 times

Benjamin (Code Monkey) - Using his elite hacking skills Benjamin can generate extra money for the cause Hacks in $100 every round

Ezili (Voodoo Monkey) - Ezili curses Bloons with dark voodoo power Beware Curses Bloons with dark voodoo power

Pat Fusty (Giant Monkey) - Pat is a huge monkey of enormous strength His unique size and power is a great asset in the war on Bloons Slams Bloons into the ground

here are currently 35 maps in Bloons Tower Defense 6 There are 12 beginner maps 11 intermediate maps 8 advanced maps and 4 expert maps The payout for completing a map depends on both the maps predetermined difficulty and the chosen game difficulty After the first completion the payout have a much smaller amount E.g An Expert Map played on Hard difficulty will give more money than a Intermediate Map played on Easy

There a large options of gamemodes for Easy Medium or hard
Easy:

Standard
Primary Monkeys Only (requires Standard to be completed)
Sandbox (requires Standard to be completed)
Deflation (requires Primary Only to be completed)
Medium:

Standard
Reverse (requires Standard to be completed)
Military Monkeys Only (requires Standard to be completed)
Apopalypse (requires Military Only to be completed)
Sandbox (requires Reverse to be completed)
Hard:

Standard
Sandbox (requires Standard to be completed)
Alternate Bloons Rounds (requires Standard to be completed)
Magic Monkeys Only (requires Standard to be completed)
Impoppable (requires Alternate Bloons Rounds to be completed)
Double HP MOABs (requires Magic Monkeys Only to be completed)
CHIMPS (requires Impoppable to be completed)

Shout outs to the BTD6 wiki/fandom for helping me with some things
and sorry for the bad English :)
https://bloons.fandom.com/wiki/Bloons_Tower_Defense_6