I know you probably don't want to copy PVZ, but I still have some ideas based on the old Isaac game ideas.
1. Add a hero baby, which can be your meat boy, Isaac, or the hero in bangbang. This hero baby can only be summoned once per level, but its ability is quite powerful. To balance the game, baby heroes need to be unlocked in specific ways.
Summoning a hero baby will cause the hero to come out of the door on the left, go to the right and fight to save the situation, especially when the player is at a disadvantage.
2. Bad drugs seem useless, and we should have other ways to use these drugs.
3. Treasure: Small dice, which can convert a turret designated by the player into a random turret of the same level. Big dice will randomly convert all the player's turrets into other turrets of the same level.
4. Promotion: Players can spend a lot of money to strengthen their turrets and make them stronger. The normal turret can shoot two tears, the mortar will randomly attack multiple targets at once, the meat block turret will turn into a meat boy to bite others, and the spiked head will be able to heal itself. etc.
5. I hope the vomiter's shape can be redrawn, he looks too much like minions.
6. New enemies
According to what I thought of in the Binding of Isaac:
Ripper: If the player kills him, his headless body will turn into a sprint or jump method to quickly charge the player, but he has very little health.
Knight: An elite who is completely immune to frontal attacks. He is only afraid of penetration, ghosts, ground thorns and melee. It is a very difficult monster in the later stage.
Meatball: He will restore the health of surrounding units by 1 tear level every few seconds. If there are more than one, he will restore it multiple times.
Blood Corpse: After being killed, it will turn into mud and resurrect. After being killed, it can only be killed by thrown weapons, ground stabs, and melee. It will flee after being killed multiple times.
Skeleton: It can only be damaged when it is moving. It cannot be damaged or hit when it is not moving. Will automatically absorb fire from "thrown" weapons, but is afraid of horizontal fire.
Long-Legged Spider: It's fast, immune to ground stings and able to get over any obstacle, but is easily killed by fire. He may be difficult to hit with a thrown weapon.
Mom's Eyes: If not repelled in time, a turret will be killed with a Mom's leg trample.
Roshan: moves slowly and is very durable. He will continuously release as if to attack the player's front line. And will crush any turret that stands in its way.
Round-headed Worm: An enhanced version of the Vomiter. It can only be attacked when it leaks out of the ground. If it is not killed, it will attack the player with bullets behind it and then hide underground. He has less health than a vomiter.
Wailer: If the player kills this monster, it will cry loudly and then die, and the surrounding enemy units will be supported by an acceleration. (The shouting skill of the first BOSS)
Leech: Appears after killing a random "elite" enemy, has little health, but is very fast.
Skeleton Boy: Every time he moves one square, he will throw a bone attack, which is slightly more powerful than ordinary enemies.
Black Goat: A very difficult enemy. It will charge quickly and has relatively strong health. At 25% health, it will enter frenzy mode. If you cannot kill him at this time, he will release brimstone fire to attack a row after a few seconds. All turrets. Each black goat can only release fire and brimstone once per life.