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

body {
  font-family: Arial, sans-serif;
  background: #f4f6f8;
  color: #1f2937;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 40px 20px;
}

.calculator {
  width: 100%;
  max-width: 700px;
  background: #ffffff;
  border-radius: 18px;
  padding: 32px;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.08);
}

h1 {
  font-size: 2rem;
  margin-bottom: 10px;
}

p {
  color: #4b5563;
  line-height: 1.5;
  margin-bottom: 24px;
}

section {
  margin-top: 28px;
}

h2 {
  font-size: 1.2rem;
  margin-bottom: 16px;
}

.calculator-form form {
  display: grid;
  gap: 16px;
}

.form-group {
  display: grid;
  gap: 8px;
}

label {
  font-weight: 600;
}

input {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid #d1d5db;
  border-radius: 10px;
  font-size: 1rem;
}

input:focus {
  outline: none;
  border-color: #2563eb;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

button {
  border: none;
  border-radius: 10px;
  padding: 14px 18px;
  font-size: 1rem;
  font-weight: 700;
  background: #111827;
  color: white;
  cursor: pointer;
  transition: transform 0.15s ease, opacity 0.15s ease;
}

button:hover {
  opacity: 0.92;
  transform: translateY(-1px);
}

button:active {
  transform: translateY(0);
}

.calculator-result {
  background: #f9fafb;
  border: 1px solid #e5e7eb;
  border-radius: 14px;
  padding: 20px;
}

.calculator-result h2 {
  margin-bottom: 0;
}

#one-rep-max {
  color: #2563eb;
  font-weight: 800;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: #ffffff;
  overflow: hidden;
  border-radius: 12px;
}

thead {
  background: #f3f4f6;
}

th,
td {
  text-align: left;
  padding: 14px 12px;
  border-bottom: 1px solid #e5e7eb;
}

th {
  font-size: 0.95rem;
}

tbody tr:last-child td {
  border-bottom: none;
}

tbody tr:hover {
  background: #f9fafb;
}

@media (max-width: 640px) {
  .calculator {
    padding: 22px;
  }

  h1 {
    font-size: 1.6rem;
  }

  th,
  td {
    padding: 12px 10px;
    font-size: 0.95rem;
  }
}