/* ==========================================================================
   STYLE.CSS - GIAO DIỆN DARK MODE TOÀN DIỆN CHO FLASHCARD APP
   ========================================================================== */

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: #121212;
    color: #e0e0e0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px;
}

/* KHUNG TỔNG CĂN GIỮA MÀN HÌNH */
.container {
    width: 100%;
    max-width: 900px;
    margin: 20px auto;
    padding: 30px;
    background-color: #1e1e1e;
    border-radius: 14px;
    border: 1px solid #2d2d2d;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.6);
}

/* HEADER & TIÊU ĐỀ */
.main-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 25px;
    flex-wrap: wrap;
    gap: 15px;
    border-bottom: 1px solid #2d2d2d;
    padding-bottom: 15px;
}

h1 {
    font-size: 1.8rem;
    color: #ffffff;
}

h2 {
    font-size: 1.4rem;
    color: #ffffff;
    margin-bottom: 15px;
}

p {
    color: #aaa;
    line-height: 1.5;
}

/* HỆ THỐNG NÚT BẤM (BUTTONS) */
button {
    font-size: 0.9rem;
    font-weight: 600;
    padding: 10px 18px;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
}

button:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

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

.btn-primary {
    background-color: #3498db;
    color: #ffffff;
}

.btn-secondary {
    background-color: #2c3e50;
    color: #ecf0f1;
}

.btn-cancel {
    background-color: #34495e;
    color: #bdc3c7;
}

.btn-report {
    background-color: #e67e22;
    color: #ffffff;
}

.btn-study {
    background-color: #2ecc71;
    color: #ffffff;
    width: 100%;
    padding: 10px;
}

/* THẺ BỘ CÂU HỎI (DECK CARDS) */
#deck-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.deck-card {
    background-color: #252525;
    border: 1px solid #333;
    border-radius: 10px;
    padding: 20px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    transition: transform 0.2s ease, border-color 0.2s ease;
}

.deck-card:hover {
    transform: translateY(-3px);
    border-color: #3498db;
}

.deck-card h3 {
    color: #ffffff;
    font-size: 1.1rem;
    margin-bottom: 8px;
}

.deck-card p {
    font-size: 0.85rem;
    color: #bbb;
    margin-bottom: 12px;
}

.badge {
    display: inline-block;
    padding: 4px 8px;
    font-size: 0.75rem;
    font-weight: bold;
    border-radius: 4px;
    background-color: #34495e;
    color: #3498db;
}

/* FORM NHẬP LIỆU */
.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    color: #ccc;
    font-size: 0.9rem;
}

input[type="text"], input[type="email"], input[type="password"], textarea, select {
    width: 100%;
    padding: 10px 14px;
    background-color: #2a2a2a;
    border: 1px solid #3d3d3d;
    color: #ffffff;
    border-radius: 6px;
    outline: none;
    font-size: 0.95rem;
    transition: border-color 0.2s ease;
}

input:focus, textarea:focus, select:focus {
    border-color: #3498db;
}

/* GIAO DIỆN MODAL HỘP THOẠI (BÁO CÁO / GÓP Ý) */
.report-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.75);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    padding: 20px;
}

.report-modal-content {
    background-color: #1e1e1e;
    border: 1px solid #333;
    padding: 25px;
    border-radius: 12px;
    width: 100%;
    max-width: 500px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.8);
}

.report-modal-content h3 {
    color: #fff;
    margin-bottom: 15px;
}

.report-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-top: 15px;
}

/* THÔNG BÁO VẮNG BÀI / LOADING */
.empty-msg {
    text-align: center;
    color: #777;
    padding: 40px 0;
    grid-column: 1 / -1;
}

#loading-indicator {
    text-align: center;
    color: #3498db;
    margin: 20px 0;
    font-weight: bold;
}