:root {
    --primary-color: #0056b3;
    --primary-hover: #004494;
    --bg-color: #f4f7f6;
    --card-bg: #ffffff;
    --text-main: #333333;
    --text-muted: #666666;
    --border-color: #ddd;
}

body {
    font-family: 'Open Sans', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
}

.container {
    max-width: 800px;
    width: 100%;
}

/* Header Styles */
.header {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 20px;
    margin-bottom: 20px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
    flex-wrap: wrap;
    text-align: center;
}

.logo {
    max-width: 250px;
    height: auto;
}

.header-text {
    font-size: 0.95rem;
    color: var(--text-muted);
    line-height: 1.5;
    text-align: left;
}

.page-title {
    text-align: center;
    color: var(--primary-color);
    margin-bottom: 30px;
}

/* Card UI */
.card {
    background-color: var(--card-bg);
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05), 0 1px 3px rgba(0, 0, 0, 0.1);
    padding: 30px;
    margin-bottom: 30px;
}

/* Form Styles */
.form-group {
    margin-bottom: 15px;
    width: 100%;
}

.form-row {
    display: flex;
    gap: 15px;
}

label {
    display: block;
    margin-bottom: 5px;
    font-weight: 600;
    font-size: 0.9rem;
}

input[type="text"], 
input[type="number"] {
    width: 100%;
    padding: 10px 15px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    box-sizing: border-box;
    font-size: 1rem;
    transition: border-color 0.3s;
}

input[type="text"]:focus, 
input[type="number"]:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 86, 179, 0.1);
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 12px 20px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    width: 100%;
    margin-top: 10px;
    transition: background-color 0.3s;
}

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

/* Results & Messages */
#message_div {
    font-weight: bold;
    margin-bottom: 15px;
    text-align: center;
}

.results-container {
    margin-top: 25px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    line-height: 1.6;
}

.grade-highlight {
    font-size: 1.2rem;
    color: var(--primary-color);
    margin-top: 10px;
}

.average-grade {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: 20px;
}

/* CSS Loader (Replaces GIF) */
#page_blocker {
    background-color: rgba(255, 255, 255, 0.8);
    z-index: 1000;
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    display: none;
    justify-content: center;
    align-items: center;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 5px solid #f3f3f3;
    border-top: 5px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Responsive adjustments */
@media (max-width: 600px) {
    .header-text { text-align: center; }
    .form-row { flex-direction: column; gap: 0; }
}

/* 1. Μετατρέπει τα γράμματα σε κεφαλαία καθώς πληκτρολογεί ο χρήστης */
#student_surname_initial_input_field,
#student_fathername_initial_input_field {
    text-transform: uppercase;
}

/* 2. Κρατάει το placeholder (το "π.χ.") ακριβώς όπως το γράψαμε στο HTML (μικρά) */
#student_surname_initial_input_field::placeholder,
#student_fathername_initial_input_field::placeholder {
    text-transform: none;
}

/* --- Εφέ "Αναπνοής" για το Λογότυπο --- */
@keyframes breathe {
    0% { transform: scale(1); filter: drop-shadow(0px 2px 4px rgba(0,0,0,0.1)); }
    50% { transform: scale(1.05); filter: drop-shadow(0px 6px 12px rgba(0,0,0,0.2)); }
    100% { transform: scale(1); filter: drop-shadow(0px 2px 4px rgba(0,0,0,0.1)); }
}

.breathing-logo {
    display: inline-block; /* Βοηθάει το browser να καταλάβει σωστά το transform */
    animation: breathe 8s infinite ease-in-out ; /* Το κάνει να κινείται συνέχεια, απαλά */
}