* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: "Segoe UI", sans-serif;
  background: #000;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.app {
  width: 100%;
  max-width: 380px;
  height: 100vh;
  background: #000;
  display: flex;
  flex-direction: column;
}

.page { display: none; flex: 1; padding: 16px; }
.page.active { display: flex; flex-direction: column; }

.screen {
  flex: 1;
  background: #050505;
  border-radius: 20px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  border: 1px solid rgba(255,215,0,0.2);
}

.result { color: gold; font-size: 32px; text-align: right; }
.history { color: rgba(255,215,0,0.5); text-align: right; }

.keys {
  margin-top: 10px;
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
}

button {
  height: 55px;
  border-radius: 14px;
  border: 1px solid rgba(255,215,0,0.2);
  background: #0a0a0a;
  color: gold;
  font-size: 16px;
  cursor: pointer;
}

button:active { transform: scale(0.95); background: #111; }

.op { color: gold; font-weight: bold; }
.equal { background: gold; color: black; grid-column: span 2; }
.clear { color: red; }

.info { color: gold; font-size: 14px; }
.info span { font-weight: bold; }

.nav { display: flex; border-top: 1px solid rgba(255,215,0,0.2); }
.nav button { flex: 1; height: 50px; background: #000; border: none; color: gold; cursor: pointer; }