:root {
    --primary-color: #3b82f6;
    --secondary-color: #1e40af;
    --success-color: #10b981;
    --error-color: #ef4444;
    --info-color: #60a5fa;
    --light-gray: #f3f4f6;
    --medium-gray: #9ca3af;
    --dark-gray: #374151;
    --white: #ffffff;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
    --fa-font-brands: normal 400 1em/1 "Font Awesome 6 Brands";
    --fa-font-regular: normal 400 1em/1 "Font Awesome 6 Free";
    --fa-font-solid: normal 900 1em/1 "Font Awesome 6 Free";
}

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

/* 确保页面占满视口高度 */
html, body {
    height: 100%;
}

body {
    background-color: #f8fafc;
    color: var(--dark-gray);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
}

header {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 1rem;
    box-shadow: var(--shadow);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
    font-weight: bold;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--white);
    font-size: 1.5rem;
    cursor: pointer;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 1.5rem;
}

nav a {
    color: var(--white);
    text-decoration: none;
    padding: 0.5rem;
    border-radius: 4px;
    transition: var(--transition);
}

nav a:hover, nav a.active {
    background-color: var(--secondary-color);
}

main {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
    flex: 1; /* 让main占据剩余空间，确保footer在底部 */
    width: 100%;
}

.module {
    background-color: var(--white);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
    width: 100%;
}

.module.hidden {
    display: none;
}

.module.active {
    border-top: 4px solid var(--primary-color);
}

.module h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--light-gray);
}

.controls {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.control-group {
    margin-bottom: 1rem;
}

.control-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.control-group input[type="range"] {
    width: 100%;
    margin-bottom: 0.5rem;
}

.control-group input[type="text"],
.control-group select {
    width: 100%;
    padding: 0.5rem;
    border: 1px solid var(--medium-gray);
    border-radius: 4px;
}

.range-value {
    text-align: center;
    font-weight: bold;
    color: var(--primary-color);
}

.checkbox-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.exercise-area {
    margin-bottom: 1.5rem;
}

.display-area {
    background-color: var(--light-gray);
    padding: 1rem;
    border-radius: 4px;
    min-height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    margin-bottom: 1rem;
}

.input-area input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--medium-gray);
    border-radius: 4px;
    font-size: 1rem;
}

.button-group {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.btn {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: var(--transition);
    font-weight: 500;
}

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

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

.btn-success {
    background-color: var(--success-color);
    color: var(--white);
}

.btn-error {
    background-color: var(--error-color);
    color: var(--white);
}

.feedback-area {
    padding: 1rem;
    border-radius: 4px;
    margin-bottom: 1rem;
    text-align: center;
    transition: var(--transition);
}

.feedback-area.success {
    background-color: rgba(16, 185, 129, 0.1);
    color: var(--success-color);
    border: 1px solid var(--success-color);
}

.feedback-area.error {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--error-color);
    border: 1px solid var(--error-color);
}

.feedback-area.info {
    background-color: rgba(96, 165, 250, 0.1);
    color: var(--info-color);
    border: 1px solid var(--info-color);
}

.stats {
    display: flex;
    justify-content: space-around;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.stat-item {
    text-align: center;
    padding: 0.5rem 1rem;
    background-color: var(--light-gray);
    border-radius: 4px;
    min-width: 100px;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--dark-gray);
}

.characters-display {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background-color: var(--light-gray);
    border-radius: 4px;
}

.characters-display h3 {
    margin-bottom: 0.5rem;
    color: var(--secondary-color);
}

.characters-display span {
    display: inline-block;
    margin: 0.25rem;
    padding: 0.25rem 0.5rem;
    background-color: var(--white);
    border-radius: 4px;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

/* 固定页脚在底部 */
footer {
    background-color: var(--dark-gray);
    color: var(--white);
    text-align: center;
    padding: 1rem;
    margin-top: auto;
    width: 100%;
}

/* 摩尔斯码参考表样式 */
.morse-chart {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-top: 1rem;
}

.chart-section-header {
    width: 100%;
    font-weight: bold;
    color: var(--primary-color);
    margin: 1rem 0 0.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--light-gray);
}

.morse-char-container {
    flex: 0 0 calc(20% - 1rem);
    min-width: 120px;
    padding: 0.75rem;
    background-color: var(--light-gray);
    border-radius: 4px;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    transition: var(--transition);
}

.morse-char-container:hover {
    background-color: #e5e7eb;
    transform: translateY(-2px);
}

.morse-char {
    font-weight: bold;
    font-size: 1.25rem;
    color: var(--primary-color);
}

.morse-code {
    font-family: monospace;
    color: var(--dark-gray);
}

.morse-code-visual {
    display: flex;
    align-items: center;
    gap: 4px;
    height: 24px;
    margin: 4px 0;
}

.morse-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--secondary-color);
}

.morse-dash {
    width: 24px;
    height: 8px;
    border-radius: 2px;
    background-color: var(--secondary-color);
}

.morse-space {
    width: 32px;
    height: 2px;
    background-color: var(--medium-gray);
    align-self: center;
}

.char-play-btn {
    background: none;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    cursor: pointer;
    padding: 4px 8px;
    border-radius: 4px;
    transition: var(--transition);
    align-self: flex-start;
}

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

/* 响应式调整 */
@media (max-width: 768px) {
    .mobile-menu-btn {
        display: block;
    }

    nav ul {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 60px;
        left: 0;
        right: 0;
        background-color: var(--primary-color);
        padding: 1rem;
        gap: 0.5rem;
        box-shadow: var(--shadow);
    }

    nav ul.active {
        display: flex;
    }

    .morse-char-container {
        flex: 0 0 calc(33.333% - 1rem);
    }

    .button-group {
        flex-direction: column;
    }

    .btn {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .morse-char-container {
        flex: 0 0 calc(50% - 1rem);
    }

    .stats {
        flex-direction: column;
    }

    .stat-item {
        width: 100%;
    }
}