/* Main layout */
*{box-sizing:border-box}
html,body{height:100%;margin:0}
body{background:#e9e9ea;color:#111;display:flex;align-items:center;justify-content:center}
.main-display{width:100%;height:100vh;display:flex;align-items:center;justify-content:center;position:relative}

/* Open button */
.open-btn{background:#1f1f1f;color:#fff;border:0;padding:12px 18px;border-radius:8px;cursor:pointer;box-shadow:0 6px 18px rgba(0,0,0,0.25)}
.open-btn:hover{transform:translateY(-2px)}

/* Modal overlay */
.modal{position:fixed;inset:0;display:flex;align-items:center;justify-content:center;background:rgba(0,0,0,0.45);opacity:0;pointer-events:none;transition:opacity .25s ease}
.modal.visible{opacity:1;pointer-events:auto}

.modal-content{background:linear-gradient(180deg,#2b2b2b,#111);color:#fff;border-radius:12px;padding:18px;min-width:320px;max-width:720px;width:90%;box-shadow:0 20px 60px rgba(0,0,0,0.6);transform:translateY(-12px) scale(.96);opacity:0;transition:transform .22s cubic-bezier(.2,.9,.2,1),opacity .22s}
.modal-content.pop{transform:translateY(0) scale(1);opacity:1}

.calc-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}
.calc-header h2{margin:0;font-size:1.1rem;color:#fff}
.close-btn{background:transparent;border:0;color:#ddd;font-size:1.1rem;cursor:pointer}

/* Calculator card */
.calculator{background:linear-gradient(180deg,#3a3a3a,#222);padding:14px;border-radius:10px;display:flex;flex-direction:column;align-items:stretch;gap:10px;width:50vw;max-width:420px}
.display{background:#0b0b0b;color:#fff;padding:12px;border-radius:8px;border:1px solid #222;font-size:1.4rem;text-align:right}

.keys{display:grid;grid-template-columns:repeat(4,1fr);gap:8px}
.btn{padding:12px 10px;border-radius:8px;border:0;background:#bdbdbd;color:#111;font-weight:600;cursor:pointer;box-shadow:inset 0 -3px 0 rgba(0,0,0,0.15)}
.btn:active{
    transform:translateY(1px)
}
.btn.num{
    background:#dcdcdc
}
.btn.op{
    background:#4a4a4a;color:#fff
}
.btn.func{
    background:#6c6c6c;color:#fff
}
.btn.equals{
    grid-column: 4;
    grid-row: 5;
    background:linear-gradient(180deg, #1a1a1a, #000);
    color: #fff;
    font-size: 1.1rem;
    box-shadow:
        inset 0  -3px 0 rgba(255, 255, 255,0.06) ,
        0 6px 14px rgba(0,0,0,0.45);
}
.btn.zero{
    grid-column:1/3
}

/* small screens */
@media (max-width:480px){
	.calculator{width:90vw}
	.modal-content{padding:12px}
}

/* subtle focus outline for accessibility */
.btn:focus,.open-btn:focus,.close-btn:focus
{outline:3px solid rgba(255,255,255,0.08);outline-offset:2px}

/* small tweak so modal-content pops from scale */
.modal-content.pop
{box-shadow:0 30px 80px rgba(0,0,0,0.6)}