:root {
    --primary-color: #4a90e2;
    --secondary-color: #f5a623;
    --background-color: #f4f4f9;
    --text-color: #333;
    --white-color: #fff;
    --correct-color: #7ed321;
    --incorrect-color: #d0021b;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    margin: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

#app {
    width: 100%;
    max-width: 480px;
    height: 100vh;
    display: flex;
    flex-direction: column;
    background-color: var(--white-color);
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
}

header {
    background-color: var(--primary-color);
    color: var(--white-color);
    padding: 1rem;
    text-align: center;
}

h1 {
    margin: 0;
    font-size: 1.5rem;
}

main {
    flex-grow: 1;
    padding: 1rem;
    overflow-y: auto;
}

#upload-section h2 {
    color: var(--primary-color);
}

#upload-section p {
    font-size: 0.9rem;
    color: #666;
}

input[type="file"],
textarea,
button {
    width: 100%;
    padding: 0.75rem;
    margin-top: 0.5rem;
    border-radius: 8px;
    border: 1px solid #ccc;
    box-sizing: border-box;
    font-size: 1rem;
}

#manual-input-area {
    margin-top: 1.5rem;
}

#word-input-table {
    border: 1px solid #ccc;
    border-radius: 8px;
    overflow: hidden;
}

.table-header, .table-row {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 5px;
    padding: 5px;
}

.table-header {
    background-color: #f0f0f0;
    font-weight: bold;
    text-align: center;
    padding: 0.5rem 5px;
}

.table-row input {
    width: 100%;
    border: 1px solid #ddd;
    border-radius: 4px;
    padding: 0.5rem;
    font-size: 0.9rem;
    box-sizing: border-box;
    margin-top: 0;
}

#add-row-btn {
    width: auto;
    padding: 0.25rem 0.75rem;
    margin-top: 0.5rem;
    font-size: 1.2rem;
    background-color: var(--secondary-color);
}

#add-row-btn:hover {
    background-color: #e0941c;
}

button {
    background-color: var(--primary-color);
    color: var(--white-color);
    border: none;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #357abd;
}

.hidden {
    display: none !important;
}

.word-card {
    background-color: #fff;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.word, .translation {
    font-size: 2rem;
    font-weight: bold;
    margin-bottom: 1.5rem;
}

.options {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

.option {
    background-color: var(--secondary-color);
}

.option:hover {
    background-color: #e0941c;
}

#spelling-input {
    text-align: center;
    margin-bottom: 1rem;
}

#spelling-result, #flashcard-result {
    margin-top: 1rem;
    font-size: 1.2rem;
    font-weight: bold;
    text-align: center;
}

.correct {
    color: var(--correct-color);
}

.incorrect {
    color: var(--incorrect-color);
}

#summary-section {
    text-align: center;
}

#accuracy-text {
    font-size: 1.2rem;
    margin: 1rem 0;
}

footer {
    background-color: #fff;
    border-top: 1px solid #eee;
}

nav {
    display: flex;
    justify-content: space-around;
}

nav button {
    flex-grow: 1;
    background: none;
    border: none;
    padding: 1rem;
    font-size: 1rem;
    color: var(--primary-color);
    cursor: pointer;
}

nav button.active {
    background-color: #eaf2fa;
    font-weight: bold;
}