:root {
    --primary-color: #46178f;
    --secondary-color: #25076b;
    --bg-color: #f2f2f2;
    --text-color: #333;
    --white: #ffffff;
    --success: #26890c;
    --error: #e21b3c;
    --option-bg: #ffffff;
    --option-hover: #e5e5e5;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

#app {
    background-color: var(--white);
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    width: 100%;
    max-width: 800px;
    min-height: 500px;
    padding: 30px;
    display: flex;
    flex-direction: column;
}

.screen {
    display: none;
    flex-direction: column;
    flex-grow: 1;
}

.screen.active {
    display: flex;
}

h2 {
    text-align: center;
    color: var(--primary-color);
    margin-bottom: 20px;
}

input[type="password"] {
    padding: 12px;
    font-size: 16px;
    border: 1px solid #ccc;
    border-radius: 4px;
    margin-bottom: 15px;
    width: 100%;
    max-width: 300px;
    align-self: center;
}

button {
    background-color: var(--primary-color);
    color: var(--white);
    border: none;
    padding: 12px 24px;
    font-size: 16px;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.2s;
    margin-bottom: 10px;
    font-weight: bold;
}

button:hover {
    background-color: var(--secondary-color);
}

.hidden {
    display: none !important;
}

.error {
    color: var(--error);
    text-align: center;
    font-size: 14px;
}

/* Selection Screen */
#units-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 10px;
    margin-bottom: 20px;
}

.unit-btn {
    background-color: var(--white);
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
    padding: 15px;
    text-align: left;
    border-radius: 6px;
    font-size: 16px;
}

.unit-btn:hover {
    background-color: rgba(70, 23, 143, 0.1);
}

.primary-btn {
    align-self: center;
    width: 100%;
    max-width: 400px;
}

/* Quiz Screen */
.header-info {
    display: flex;
    justify-content: space-between;
    font-weight: bold;
    margin-bottom: 15px;
    color: var(--primary-color);
    font-size: 18px;
}

.progress-container {
    background-color: #e0e0e0;
    height: 10px;
    border-radius: 5px;
    margin-bottom: 5px;
    overflow: hidden;
}

#progress-bar {
    background-color: var(--primary-color);
    height: 100%;
    width: 0%;
    transition: width 0.3s ease;
}

.progress-text {
    text-align: center;
    font-size: 14px;
    color: #666;
    margin-bottom: 20px;
}

.card {
    background-color: var(--white);
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

#question-text {
    font-size: 22px;
    margin-bottom: 25px;
    text-align: center;
}

#options-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    margin-bottom: 20px;
}

.option-btn {
    background-color: var(--option-bg);
    color: var(--text-color);
    border: 2px solid #ccc;
    padding: 15px;
    font-size: 16px;
    border-radius: 6px;
    text-align: left;
    transition: all 0.2s;
    font-weight: normal;
}

.option-btn:hover:not(:disabled) {
    background-color: var(--option-hover);
    border-color: #aaa;
}

.option-btn.correct {
    background-color: var(--success) !important;
    border-color: var(--success) !important;
    color: var(--white);
}

.option-btn.incorrect {
    background-color: var(--error) !important;
    border-color: var(--error) !important;
    color: var(--white);
}

.option-btn:disabled {
    cursor: default;
    opacity: 0.8;
}

#next-btn, #finish-btn {
    align-self: center;
    margin-top: auto;
}

/* Results Screen */
.score-result {
    font-size: 24px;
    text-align: center;
    margin: 30px 0;
    font-weight: bold;
}

#feedback-message {
    text-align: center;
    font-size: 18px;
    margin-bottom: 30px;
}