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HTML 

              
                <div class="min-h-screen p-16 bg-gray-100">


<div
	x-data="calculator()"
	@keydown.window.tab="usedKeyboard = true">
	
	<h1 class="font-bold text-xl mb-2" id="title">A Calculator</h1>
    <div
        role="application"
        aria-labelledby="title"
        style="max-width:396px"
        class="bg-gray-200">
        <div class="relative">
            <div
				aria-live="polite"
				x-text="formula"
				class="absolute top-0 right-0 text-green-400 font-bold pt-2 pr-4"></div>
            <div
                aria-live="polite"
				aria-atomic="true"
                style="background:#282828"
                class="h-32 w-full text-white text-6xl flex items-center pt-8 pr-5 justify-end mb-1">
                <span class="sr-only">The total is:</span>
				<span x-text="total"></span>
            </div>
        </div>
        <div @click="updateTotal($event.target.value)" class="flex space-x-1">
            <div id="controls" class="gap-1 grid grid-cols-1">
                <button
                    value=''
                    class="text-3xl h-24 w-24 flex items-center justify-center bg-green-400 hover:bg-green-500"
					:class="{'focus:outline-none': !usedKeyboard}"
                    aria-label="Clear all">
                    C
                </button>
                <button
                    value='BS'
                    class="text-3xl h-24 w-24 flex items-center justify-center bg-green-400 hover:bg-green-500"
					:class="{'focus:outline-none': !usedKeyboard}"
                    aria-label="Backspace">
                    BS
                </button>
                <button
                    value='+'
                    class="text-3xl h-24 w-24 flex items-center justify-center bg-green-400 hover:bg-green-500"
					:class="{'focus:outline-none': !usedKeyboard}"
                    aria-label="Add">
                    +
                </button>
                <button
                    value='-'
                    class="text-3xl h-24 w-24 flex items-center justify-center bg-green-400 hover:bg-green-500"
					:class="{'focus:outline-none': !usedKeyboard}"
                    aria-label="Subtract">
                    -
                </button>
            </div>
            <div id="buttons" class="gap-1 grid grid-cols-3">
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="9">9</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="8">8</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="7">7</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="6">6</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="5">5</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="4">4</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="3">3</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="2">2</button>
                <button
					class="text-3xl h-24 w-24 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="1">1</button>
                <button
					class="text-3xl h-24 col-span-3 bg-gray-400 hover:bg-gray-300"
					:class="{'focus:outline-none': !usedKeyboard}"
					value="0">0</button>
            </div>
        </div>
    </div>
	
</div>
	
	
	
	
	
	
</div>
!

CSS 

              
                [x-cloak] { display: none; }
!

JS 

              
                function calculator() {
	return {
		usedKeyboard: false,
		formula: '',
		updateTotal(nextInput) {
			if (this.startsWithOperator(nextInput)) return
			if (this.hasDoubleOperators(nextInput)) return

			if (nextInput === 'BS') {
				// Baackspace
				this.formula = this.formula.slice(0, -1)
			} else if (nextInput === '') {
				// Clear
				this.formula = ''
			} else {
				this.formula = this.formula + nextInput
			}
			
		},
		get total() {
            let total = 0
			let temp
            temp = this.formula.match(/[+\-]*(\.\d+|\d+(\.\d+)?)/g) || []
            while (temp.length) {
                total += parseFloat(temp.shift())
            }
            return total
        },
		hasDoubleOperators(nextInput) {
			return ['+', '-'].includes(nextInput.slice(-1)) && ['+', '-'].includes(this.formula.slice(-1))
		},
		startsWithOperator(nextInput) {
			return ['+', '-'].includes(nextInput) && !this.formula.length
		}
	}
}
!
999px

Console