:root {
  --bg-body: #ededed;
  --bg-calc: #ffffff;
  --text-primary: #000000;
  --btn-bg: #f2f2f2;
  --btn-bg-hover: #e6e6e6;
  --btn-op-bg: #dcdcdc;
  --btn-op-bg-hover: #d0d0d0;
  --btn-op-text: #000000;
  --btn-equal-bg: #000000;
  --btn-equal-text: #ffffff;
  --btn-equal-hover: #333333;
  --border-color: #d1d1d1;
  --shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
}

body.dark {
  --bg-body: #000000;
  --bg-calc: #121212;
  --text-primary: #ffffff;
  --btn-bg: #1f1f1f;
  --btn-bg-hover: #2a2a2a;
  --btn-op-bg: #333333;
  --btn-op-bg-hover: #404040;
  --btn-op-text: #ffffff;
  --btn-equal-bg: #ffffff;
  --btn-equal-text: #000000;
  --btn-equal-hover: #e6e6e6;
  --border-color: #333333;
  --shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
}

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
  font-family: "Inter", sans-serif;
  outline: none;
  user-select: none;
  transition:
    background-color 0.4s ease,
    color 0.2s ease,
    border-color 0.4s ease,
    box-shadow 0.4s ease;
}

body {
  background-color: var(--bg-body);
  height: 100vh;
  width: 100vw;
  display: flex;
  justify-content: center;
  align-items: center;
}

.calculator {
  position: relative;
  width: 320px;
  padding: 20px;
  border-radius: 30px;
  background-color: var(--bg-calc);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.theme-toggler {
  position: absolute;
  top: 25px;
  right: 25px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  cursor: pointer;
  background-color: var(--btn-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}

.theme-toggler::before {
  content: "";
  height: 12px;
  width: 12px;
  border-radius: 50%;
  background-color: var(--text-primary);
}

.display-screen {
  width: 100%;
  height: 130px;
  margin-bottom: 10px;
  display: flex;
  align-items: flex-end;
  justify-content: flex-end;
  padding: 10px 5px;
  overflow: hidden;
}

#display {
  font-size: 3.5rem;
  font-weight: 500;
  word-wrap: break-word;
  word-break: break-all;
  text-align: right;
  color: var(--text-primary);
  letter-spacing: -2px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

button {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 50%;
  border: none;
  font-size: 1.3rem;
  font-weight: 500;
  cursor: pointer;
  background-color: var(--btn-bg);
  color: var(--text-primary);
  display: flex;
  justify-content: center;
  align-items: center;
  transition:
    transform 0.1s ease,
    background-color 0.2s;
}

button:active {
  transform: scale(0.92);
}

button:hover {
  background-color: var(--btn-bg-hover);
}

.btn-operator {
  background-color: var(--btn-op-bg);
  color: var(--btn-op-text);
  font-size: 1.4rem;
}

.btn-operator:hover {
  background-color: var(--btn-op-bg-hover);
}

.btn-equal {
  grid-column: 4 / 5;
  grid-row: 4 / 6;
  height: 100%;
  aspect-ratio: auto;
  border-radius: 35px;
  background-color: var(--btn-equal-bg);
  color: var(--btn-equal-text);
  font-size: 1.5rem;
}

.btn-equal:hover {
  background-color: var(--btn-equal-hover);
}