Game Design#2: Tetris battle clone

Game Concept:
4-block puzzle (tetris clone) with multiplayer component. Spice things up with in-app purchase effect and items

Game Mechanic:
Easy. Tetris.
With more effect like send a row of random blocks to opponent. A bomb to clear part of the screen, etc.

Fun Factor:
RPG-style advancement. Keep winning to collect XP and earn more gold. Use gold to buy one-time item. Use XP to upgrade skills.
Leaderboard/Ladder system for competitive player.
Live streaming game for audience to enjoy.
Chatroom, of course.
Sticker system for more immerse chat environment.

Art direction:
Just a block. Maybe 3d-feel blocks.

Business model:
Free to play with in-app purchase.
Pay to win kind of game