:root {
    --primary-color: #007AFF;
    --success-color: #6BCB77;
    --warning-color: #FF293D;
    --star-color: #FFD93D;
    --light-gray: #f4f7f6;
    --dark-gray: #333;
}

body {
    font-family: 'Poppins', sans-serif;
    text-align: center;
    margin: 0;
    padding: 20px;
    background: linear-gradient(135deg, #f4f7f6, #d4dde1);
    color: var(--dark-gray);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

.top-bar {
    position: absolute;
    top: 10px;
    right: 10px;
}

.screen {
    width: 100%;
}

.quiz-container, .report-container {
    background: #fff;
    padding: 30px;
    border-radius: 16px;
    width: 100%;
    max-width: 450px;
    box-sizing: border-box;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    margin: 0 auto;
}

h1 {
    font-family: 'Acme', sans-serif;
    font-weight: 700;
}

.quiz-container h1 {
    color: var(--primary-color);
}

.report-container h1 {
    color: var(--success-color);
}

.question-form {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    margin-bottom: 20px;
}

.question-text {
    font-family: 'Acme', sans-serif;
    font-size: 2.5em;
    font-weight: 600;
}

.question-form input[type="number"] {
    margin-top: 0;
}

input[type="number"] {
    font-family: 'Poppins', sans-serif;
    font-size: 1.5em;
    width: 120px;
    text-align: center;
    border: 2px solid #ddd;
    border-radius: 8px;
    padding: 5px;
    transition: border-color 0.3s;
    -moz-appearance: textfield;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type="number"]:focus {
    outline: none;
    border-color: var(--primary-color);
}

.btn, button {
    font-family: 'Poppins', sans-serif;
    font-size: 1em;
    font-weight: 600;
    padding: 12px 25px;
    margin-top: 20px;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    text-decoration: none;
    display: inline-block;
    transition: transform 0.2s, background-color 0.2s;
}

.btn:hover, button:hover {
    transform: translateY(-2px);
}

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

.timer { margin-top: 15px; font-size: 1.2em; color: #555; }

.progress-container {
    width: 100%;
    background-color: #f3f3f3;
    border: 1px solid #ddd;
    border-radius: 5px;
    margin-top: 20px;
}

.restart-btn {
    background-color: var(--warning-color);
    color: white;
    margin-top: 15px;
}

.stars-container {
    margin-bottom: 15px;
    display: flex;
    justify-content: space-between;
    font-size: clamp(1.6em, 5vw, 2em);
}

.star-filled { color: var(--star-color); }
.star-outline { color: #ccc; }

.progress-bar {
    height: 24px;
    background-color: var(--success-color);
    text-align: center;
    line-height: 24px;
    color: white;
    border-radius: 5px;
    transition: width 0.3s ease-in-out;
}

.operation-selection button {
    font-size: 2em;
    width: 60px;
    height: 60px;
    margin: 10px;
}

.language-btn {
    position: relative;
    background-color: transparent;
    border: none;
    font-size: 2em;
    padding: 5px;
    margin-top: 0;
    color: var(--dark-gray);
}

.language-btn:hover::after {
    content: attr(data-tooltip);
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    background-color: #333;
    color: white;
    padding: 5px 10px;
    border-radius: 5px;
    font-size: 0.5em;
    white-space: nowrap;
    margin-top: 5px;
    z-index: 10;
}

@media (max-width: 480px) {
    body {
        padding: 10px;
        align-items: flex-start;
        padding-top: 2vh;
    }

    .quiz-container, .report-container {
        padding: 20px;
    }

    .question-text {
        font-size: 2em;
    }

    input[type="number"] {
        font-size: 1.3em;
        width: 100px;
    }
}