In javascript html, and css I am making a tower defense game, how would I make it so I can purchase my tower and then place it within the game box.

here is my tower code:

#Tower_1{

width: 30px:

Height: 30px:

background color: blue:

}

Here is a example of what I want, so the blue square is my tower, the grey rectangle is the tower shop, and the green is the price of the tower, how would I buy the tower and make sure it does not go outside the box and only stay in the box area.

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