/* ===============================
   LIGHT THEME VARIABLES (default)
   =============================== */
:root {
  --bg: linear-gradient(135deg, #f0f4f8, #d9e4f5);
  --text: #1c1c1e;
  --card-bg: rgba(255, 255, 255, 0.85);
  --input-bg: #ffffff;
  --label-color: #555;
  --accent: #3366cc;
  --btn-bg: #3366cc;
  --btn-text: #fff;
  --blur: blur(8px);
}

/* ===============================
   DARK MODE VARIABLES (toggle)
   =============================== */
#theme-toggle:checked ~ .wrapper {
  --bg: linear-gradient(135deg, #121212, #1c1c1e);
  --text: #f1f1f1;
  --card-bg: rgba(30, 30, 30, 0.9);
  --input-bg: #2c2c2e;
  --label-color: #ccc;
  --accent: #4f8cff;
  --btn-bg: #4f8cff;
  --btn-text: #fff;
}

/* ===============================
   RESET & BASE STYLES
   =============================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: "Segoe UI", sans-serif;
  background: var(--bg);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  transition: background 0.4s ease, color 0.4s ease;
  color: var(--text);
  padding: 1rem;
}
.wrapper {
  width: 100%;
}

/* ===============================
   HEADER STYLES
   =============================== */
.container {
  max-width: 400px;
  margin: 0 auto;
}
header {
  margin-bottom: 2rem;
}
.back-button {
  text-decoration: none;
  display: inline-block;
  margin-bottom: 10px;
  padding: 6px 14px;
  background: var(--btn-bg);
  color: var(--btn-text);
  border-radius: 5px;
  font-size: 0.9rem;
  transition: background 0.3s ease;
}
.back-button:hover {
  background: var(--accent);
  color: #fff;
}
.theme-toggle {
  float: right;
  cursor: pointer;
  background: var(--btn-bg);
  color: var(--btn-text);
  padding: 6px 10px;
  border-radius: 5px;
  transition: background 0.3s;
}
.theme-toggle:hover {
  background: var(--accent);
  color: #fff;
}
.challenge-title {
  font-size: 1.4rem;
  margin-top: 0.5rem;
}
.challenge-desc {
  font-size: 0.9rem;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(4px);
  border-left: 4px solid var(--accent);
  padding: 10px 15px;
  border-radius: 6px;
  margin-top: 10px;
}

/* ===============================
   LOGIN FORM STYLES
   =============================== */
.login-form {
  background: var(--card-bg);
  backdrop-filter: var(--blur);
  padding: 30px;
  border-radius: 12px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.2);
  transition: all 0.4s ease;
}
.login-form h2 {
  text-align: center;
  margin-bottom: 25px;
  font-weight: 500;
  color: var(--text);
}
.form-group {
  position: relative;
  margin-bottom: 25px;
}
.login-form input {
  width: 100%;
  padding: 10px 10px;
  background: var(--input-bg);
  border: none;
  border-bottom: 2px solid #ccc;
  outline: none;
  color: var(--text);
  transition: border-color 0.3s ease, background 0.3s ease;
}
.login-form input:focus {
  border-color: var(--accent);
}
.login-form label {
  position: absolute;
  left: 10px;
  top: 10px;
  color: var(--label-color);
  pointer-events: none;
  transition: all 0.3s ease;
  background: transparent;
}
.login-form input:focus + label,
.login-form input:valid + label {
  top: -10px;
  font-size: 0.8rem;
  color: var(--accent);
}
.login-form button {
  width: 100%;
  padding: 10px;
  background: var(--btn-bg);
  color: var(--btn-text);
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-weight: bold;
  transition: background 0.3s ease;
}
.login-form button:hover {
  background: var(--accent);
  color: #fff;
}

/* ===============================
   RESPONSIVE
   =============================== */
@media (max-width: 480px) {
  .challenge-desc {
    font-size: 0.85rem;
  }
  .login-form {
    padding: 20px;
  }
}