/* ---------- CSS Variables (themes) ---------- */
:root {
    --bg-color: #121212;
    --text-color: #ffffff;
    --form-bg: #1e1e1e;
    --input-border: #555;
    --label-color: #aaa;
    --label-focus-color: #00b4d8;
    --button-bg: linear-gradient(135deg, #007bff, #00b4d8);
    --button-text: #ffffff;
}

/* Theme radio buttons effect */
#dark:checked ~ .container,
#dark:checked ~ .container form,
#dark:checked ~ .container * {
    --bg-color: #121212;
    --text-color: #ffffff;
    --form-bg: #1e1e1e;
    --input-border: #555;
    --label-color: #aaa;
    --label-focus-color: #00b4d8;
}

#light:checked ~ .container,
#light:checked ~ .container form,
#light:checked ~ .container * {
    --bg-color: #f8fbfd;
    --text-color: #333;
    --form-bg: #ffffff;
    --input-border: #ccc;
    --label-color: #888;
    --label-focus-color: #007bff;
}

#blue:checked ~ .container,
#blue:checked ~ .container form,
#blue:checked ~ .container * {
    --bg-color: #001f3f;
    --text-color: #e0f7ff;
    --form-bg: #003366;
    --input-border: #007bff;
    --label-color: #a0d4ff;
    --label-focus-color: #00b4d8;
}

/* ---------- Global Layout ---------- */
body {
    font-family: 'Poppins', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

/* Navbar */
nav {
    width: 100%;
    padding: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(0,0,0,0.2);
    backdrop-filter: blur(5px);
    box-sizing: border-box;
}

.nav-btn {
    text-decoration: none;
    color: var(--text-color);
    font-weight: bold;
    padding: 0.5rem 1rem;
    border: 1px solid var(--text-color);
    border-radius: 8px;
    transition: 0.3s;
}

.nav-btn:hover { background: var(--text-color); color: var(--bg-color); }

/* Theme picker */
.theme-picker input { display: none; }
.theme-picker label {
    width: 24px; height: 24px;
    border-radius: 50%;
    display: inline-block;
    margin-left: 0.5rem;
    cursor: pointer;
    border: 2px solid #fff;
}
.theme-picker label.dark { background: #121212; }
.theme-picker label.light { background: #f8fbfd; }
.theme-picker label.blue { background: #003366; }

/* Container */
.container { text-align: center; margin-top: 2rem; }

/* Typewriter header */
.typewriter h1 {
    overflow: hidden;
    border-right: 3px solid var(--label-focus-color);
    white-space: nowrap;
    margin: 0 auto 2rem;
    font-size: 2rem;
    letter-spacing: 2px;
    width: 0;
    animation: typing 4s steps(20, end), blink 0.75s step-end infinite;
}
@keyframes typing { from { width:0; } to { width:100%; } }
@keyframes blink { 0%,100%{border-color:transparent;} 50%{border-color:var(--label-focus-color);} }

/* Form */
form {
    background: var(--form-bg);
    padding: 2rem;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
    width: 100%;
    max-width: 420px;
    margin: 0 auto;
    box-sizing: border-box;
}

/* Inputs */
.input-group { position: relative; margin-bottom: 1.5rem; }
.input-group input,
.input-group textarea {
    width: 100%;
    padding: 1rem 0.75rem 0.5rem;
    border: 1px solid var(--input-border);
    border-radius: 8px;
    font-size: 1rem;
    outline: none;
    background: transparent;
    caret-color: var(--label-focus-color);
    color: var(--text-color);
    box-sizing: border-box;
}
.input-group label {
    position: absolute;
    top: 1rem;
    left: 0.75rem;
    color: var(--label-color);
    pointer-events: none;
    transition: 0.3s ease;
    background: var(--form-bg);
    padding: 0 4px;
}
.input-group input:focus + label,
.input-group input:not(:placeholder-shown) + label,
.input-group textarea:focus + label,
.input-group textarea:not(:placeholder-shown) + label {
    top: -0.6rem;
    left: 0.6rem;
    font-size: 0.8rem;
    color: var(--label-focus-color);
}

/* Button */
button {
    width: 100%;
    padding: 0.8rem;
    background: var(--button-bg);
    border: none;
    border-radius: 8px;
    color: var(--button-text);
    font-size: 1rem;
    cursor: pointer;
    transition: transform 0.15s ease, box-shadow 0.2s ease;
}
button:hover { transform: translateY(-2px); box-shadow: 0 4px 10px rgba(0,123,255,0.3); }
button:active { transform: scale(0.96); box-shadow: 0 0 5px rgba(0,123,255,0.4); }

/* Responsive */
@media (max-width:600px){
    form { padding:1.5rem; margin:0 1rem; }
    .typewriter h1 { font-size:1.5rem; }
    button { font-size:0.95rem; }
}