This is a really important topic. Think of a boat with holes. Overtime your game has something that is hard to understand, it's like a new hole to the boat. If it's too big or there's too many, your boar will sink and the player will leave the game.
To avoid these prefer intuitive and clear approaches which require minimal if none explanation.
The players will not do what you expect.
The players will do the wrong things.
Players are not logical and will not understand the things that are very clear to you.
I often notice designers don't care about player's not in their target group or not like them.
Do you really wanna loose like 15% or 50% of your players?
With small adjustments and clarification you do a lot and keep your retention much higher! Focus on making absolute sure all the players
Tutorial is the part of the game that teaches and guides your player to the game.
What does Tetris use to clarify the game to the player?
It shows you the next piece during gameplay. This is essential for you to be able to plan even your current piece.
All shapes have different color. If you'd try this with them all having the same color, might get difficult.
The shapes are outlined even inside the shape like creating the 4 squares in the Tetris piece on the left. This helps identifying where each piece goes.
Here's a game that will be the bases for the next 3 exercises. The exercises are on a real game we worked on.
The game has following power-ups & stunt features: