This is a super simple game to keep kids focused on vocabulary cards. Review and check the vocabulary cards posted on the blackboard. Have the students close their eyes. Draw a bomb under one or two of the cards. You can choose to write points under the other cards such as +3 or +1 (if you're feeling extra sassy, you can write negative points as well -1 or -2). When you finish writing the hidden numbers and bombs, have the students open their eyes and choose one student to say a card on the board. Make a show out of revealing what's underneath the card. After revealing every card you can total the points, make a show of losing or winning to the kids and then move on to the next activity.
I play that bombs reset the students' points, but you could make the bombs worth 100 points or something crazy. This would keep the game more positive. Sometimes if you make the bomb reset the points, the shy student that picks the bomb can get upset.
I wouldn't recommend this as a speaking activity - just something to keep the kids entertained as you practice vocabulary.
You can add a call and response to the activity as well. For example, you can have the students ask "What animals do you like?" and the answering student responds with "I like (card on the board)!"
Alternative: I've also switched up this game and framed it as "The Character Game." Instead of drawing bombs and points you can put some of the kids' favorite characters like doraemon, anpanman, etc. underneath the cards. The students enjoy the surprise of seeing what's behind the card while getting to practice vocabulary.
There is already a different game known to Japanese kids called ばくだんゲーム (Bomb Game - like Hot Potato where you pass the bomb around the circle with a timer counting down) so I would recommend changing the name and theme. I like the concept though!