At first i was " what a simple concept"
But now i'm really amazed by the game. The style is lovely. The tittle art matches the game wonderfully and is in a colorscheme i usually say is overused, but this one just is so well made and special. I love it.
And i love how it sorta changes into a fun idle game once you get enough trap uprgades. I'd say traps need further upgrades. Make it expensive, make it a class to spend on if i prefer this style.
Game needs some chill music to matchi. Also the mute button on the left didnt work for me.
But i got to the end of the upgrade tree in 15 minutes i guess. I loved the pace' so making more grindy would be bad. Splash in unskippable cosmetic upgraded with witty explanations, like having to add background elements to attract other colour ghosts. Ghost expression variations. Nametagged ghost of a specific color for a collectable system, splash in some story to them.
Theres really a lot of potential for this game and i don't say that lightly. Its a really good start, but needs content. A lot of potential to be a big hit. Work on it dude' you're almost there.