:root {
    --pink-dark: #FF5E7E;
    --pink-medium: #FF8EA4;
    --pink-light: #FFF0F2;
    --pink-bg: #FFF8F9;
    --coral: #FF7B93;
    --text-color: #5D4347;
    --white: #FFFFFF;
    --shadow-soft: 0 8px 24px rgba(255, 142, 164, 0.12);
    --shadow-hover: 0 12px 30px rgba(255, 94, 126, 0.2);
    --border-radius-lg: 24px;
    --border-radius-sm: 16px;
}

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

body {
    font-family: 'Nunito', 'Segoe UI', sans-serif;
    background-color: var(--pink-bg);
    color: var(--text-color);
    line-height: 1.6;
    padding: 20px;
}

.container {
    max-width: 950px;
    margin: 0 auto;
    padding: 10px;
}

/* Header ngọt ngào */
.header {
    text-align: center;
    background: linear-gradient(135deg, #FFE4E8, #FFF0F2);
    padding: 35px 20px;
    border-radius: var(--border-radius-lg);
    border: 3px dashed var(--pink-medium);
    margin-bottom: 30px;
    position: relative;
    box-shadow: var(--shadow-soft);
}

.header h1 {
    color: var(--pink-dark);
    font-size: 2.3rem;
    margin-bottom: 12px;
    font-weight: 800;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.05);
}

.header p {
    font-size: 1.15rem;
    color: #7D5D62;
    font-weight: 600;
}

.section-title {
    color: var(--pink-dark);
    font-size: 1.55rem;
    margin: 35px 0 15px 0;
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 800;
}

/* Thẻ nội dung Card */
.card {
    background-color: var(--white);
    border-radius: var(--border-radius-lg);
    padding: 25px;
    margin-bottom: 25px;
    box-shadow: var(--shadow-soft);
    border: 2px solid #FFEBEF;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
}

/* Lưới các chủ đề */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 18px;
    margin-top: 15px;
}

.grid-item {
    background: var(--pink-light);
    border-radius: var(--border-radius-sm);
    padding: 18px;
    border: 1px solid #FFD3DB;
}

.grid-item h3 {
    color: var(--pink-dark);
    font-size: 1.15rem;
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* List dễ thương */
ul {
    list-style: none;
}

li {
    margin-bottom: 8px;
    position: relative;
    padding-left: 25px;
    font-size: 0.98rem;
}

li::before {
    content: "🌸";
    position: absolute;
    left: 0;
    top: 2px;
    font-size: 0.9rem;
}

/* Bảng Động Từ Thông Thái */
.verb-table-container {
    overflow-x: auto;
    margin-top: 15px;
    border-radius: var(--border-radius-sm);
    border: 2px solid #FFEBEF;
}

.verb-table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
    font-size: 0.95rem;
    background-color: var(--white);
}

.verb-table th {
    background-color: #FFE4E8;
    color: var(--pink-dark);
    font-weight: 700;
    padding: 15px;
    border-bottom: 2px solid #FFD3DB;
    vertical-align: top;
}

.verb-table td {
    padding: 15px;
    border-bottom: 1px solid #FFF0F2;
    vertical-align: top;
}

.verb-table tr:nth-child(even) {
    background-color: #FFFDFD;
}

.verb-table tr:hover {
    background-color: #FFF5F6;
}

.tense-badge {
    display: inline-block;
    font-size: 0.78rem;
    padding: 2px 8px;
    border-radius: 12px;
    font-weight: bold;
    margin-bottom: 4px;
}
.badge-present { background-color: #E2F0D9; color: #385723; }
.badge-continuous { background-color: #DDEBF7; color: #1F4E78; }
.badge-past { background-color: #FFF2CC; color: #7F6000; }

.signal-box {
    display: block;
    background-color: #FFF0F2;
    border: 1px dashed var(--pink-medium);
    border-radius: 8px;
    padding: 6px 10px;
    margin-top: 8px;
    font-size: 0.8rem;
    font-weight: 600;
    color: #C2415A;
    line-height: 1.3;
}

/* Tab gập mở ôn tập tương tác */
details {
    background: var(--white);
    border-radius: var(--border-radius-sm);
    margin-bottom: 12px;
    border: 2px solid #FFEBEF;
    box-shadow: var(--shadow-soft);
    overflow: hidden;
}

summary {
    padding: 15px 20px;
    font-weight: 700;
    color: var(--pink-dark);
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: linear-gradient(135deg, #FFF5F6, #FFF);
    font-size: 1.05rem;
}

summary::after {
    content: "✨";
    font-size: 1.1rem;
}

details[open] summary::after {
    content: "💖";
}

.details-content {
    padding: 20px;
    border-top: 1px solid #FFEBEF;
    background-color: var(--white);
}

.badge {
    background-color: var(--pink-medium);
    color: var(--white);
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 700;
    display: inline-block;
    margin-bottom: 5px;
}

/* Thử tài luyện tập */
.quiz-box {
    background-color: #FFF9FA;
    border-left: 5px solid var(--pink-dark);
    padding: 15px;
    border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
    margin-bottom: 15px;
}

.quiz-box p {
    font-weight: bold;
    margin-bottom: 8px;
}

.answer-reveal {
    background-color: #E6F7ED;
    color: #2D6A4F;
    padding: 8px 12px;
    border-radius: 8px;
    margin-top: 8px;
    font-size: 0.92rem;
    border: 1px solid #C7F9CC;
}

.btn {
    display: inline-block;
    background-color: var(--pink-dark);
    color: var(--white);
    padding: 10px 22px;
    border-radius: 25px;
    text-decoration: none;
    font-weight: 700;
    margin-top: 15px;
    box-shadow: 0 4px 10px rgba(255, 94, 126, 0.25);
    transition: all 0.3s ease;
}

.btn:hover {
    background-color: #E04E6C;
    transform: scale(1.03);
}

.footer {
    text-align: center;
    margin-top: 50px;
    color: #8A7376;
    font-size: 0.9rem;
    padding: 20px;
    border-top: 2px dashed #FFE0E5;
}

/* Ribbon xinh xắn */
.ribbon {
    position: absolute;
    top: 15px;
    left: -10px;
    background-color: #FFC0CB;
    color: #5D4347;
    padding: 4px 15px;
    font-weight: 700;
    border-radius: 0 5px 5px 0;
    box-shadow: 2px 2px 5px rgba(0,0,0,0.08);
    font-size: 0.85rem;
}

.note-box {
    background-color: #FFFEE6;
    border: 1px solid #FFE57F;
    padding: 12px;
    border-radius: 12px;
    font-size: 0.92rem;
    margin-top: 15px;
}