Spiked Trench

as the title suggest i would suggest to implement new defensive building block named spiked trench,

size 1x1 block as wall size
cost 1/2 of the price of wall (gold and elixir to purchase)
build time 0
number of blocks available 1/3 of wall blocks
number of levels 4
available on TH7 and up
at lvl 1 - goblins can't pass over
at lvl 2 - goblins and barbarians can't pass
at lvl 3 - gobo, barb, arch and wizz can't pass
at lvl 4 - giants, valky, hog riders and witch can't pass

inafective vs pekka, golem and heroes, only does small amount of dmg to those units and slows them down for 5 sec

usage: to build funneling parts to lure troops to traps and to protect vulnerable parts of defenses

edit: spiked trench cannot form enclosed part as wall's do, if building box element it should have 2 blocks without trench, otherwise some could trench up TH or similar ....