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

body {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    max-width: 800px;
    width: 100%;
    background: white;
    border-radius: 16px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

.app-header {
    background: linear-gradient(135deg, #4b6cb7 0%, #182848 100%);
    color: white;
    padding: 30px;
    text-align: center;
}

.app-header h1 {
    font-size: 2.2rem;
    margin-bottom: 10px;
}

.app-header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

.content {
    padding: 30px;
    min-height: 400px;
    display: flex;
    flex-direction: column;
}

.intro-screen, .challenge-screen {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    flex-grow: 1;
}

.intro-screen button, .btn-complete {
    margin: 30px auto 0 auto;
    display: block;
}

.intro-screen h2 {
    color: #2c3e50;
    margin-bottom: 20px;
    font-size: 1.8rem;
}

.intro-screen p {
    color: #555;
    line-height: 1.6;
    margin-bottom: 30px;
    max-width: 600px;
}

.btn {
    background: linear-gradient(135deg, #4b6cb7 0%, #182848 100%);
    color: white;
    border: none;
    padding: 14px 30px;
    font-size: 1.1rem;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.3s, box-shadow 0.3s;
    font-weight: 600;
    margin-top: 10px;
}

.btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 7px 15px rgba(0, 0, 0, 0.1);
}

.btn-complete {
    background: linear-gradient(135deg, #2ecc71 0%, #27ae60 100%);
}

.btn-reset {
    background: none;
    border: 1px solid #e74c3c;
    color: #e74c3c;
    padding: 4px 8px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.8rem;
    margin-left: 10px;
    transition: all 0.3s;
}

.btn-reset:hover {
    background: #e74c3c;
    color: white;
}

.challenge-header {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin-bottom: 30px;
    align-items: center;
}

.day-indicator {
    background: #4b6cb7;
    color: white;
    padding: 8px 20px;
    border-radius: 50px;
    font-weight: bold;
}

.progress {
    font-size: 0.9rem;
    color: #7f8c8d;
}

.challenge-card {
    background: #f8f9fa;
    border-radius: 12px;
    padding: 30px;
    width: 100%;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
    margin-bottom: 20px;
}

.challenge-title {
    color: #2c3e50;
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.challenge-description {
    color: #555;
    line-height: 1.6;
    margin-bottom: 20px;
}

.challenge-tip {
    background: #e8f4fc;
    border-left: 4px solid #4b6cb7;
    padding: 15px;
    border-radius: 4px;
    margin-top: 20px;
    font-style: italic;
}

.completion-message {
    background: #d4edda;
    color: #155724;
    padding: 15px;
    border-radius: 8px;
    margin-top: 20px;
    display: none;
}

.info-footnote {
    margin-top: 25px;
    padding-top: 15px;
    border-top: 1px solid #e0e0e0;
    text-align: center;
}

.info-footnote a {
    color: #4b6cb7;
    text-decoration: none;
    font-size: 0.9rem;
    transition: color 0.3s;
}

.info-footnote a:hover {
    color: #182848;
    text-decoration: underline;
}

.navigation {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin-top: 20px;
}

.btn-prev {
    background: #95a5a6;
}

.hidden {
    display: none;
}

@media (max-width: 600px) {
    .container {
        border-radius: 10px;
    }

    .app-header {
        padding: 20px;
    }

    .app-header h1 {
        font-size: 1.8rem;
    }

    .content {
        padding: 20px;
    }

    .challenge-card {
        padding: 20px;
    }
}