/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.hidden {
    display: none !important;
}

:root {
    --primary-color: #4a90d9;
    --primary-dark: #357abd;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --error-color: #dc3545;
    --warning-color: #ffc107;
    --background: #f8f9fa;
    --card-bg: #ffffff;
    --text-color: #333333;
    --text-muted: #6c757d;
    --border-color: #dee2e6;
    --code-bg: #f4f4f4;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

/* Dark theme */
body.dark-theme {
    --primary-color: #6ba3e0;
    --primary-dark: #5a93d0;
    --secondary-color: #8e9aa5;
    --success-color: #4caf50;
    --error-color: #f44336;
    --warning-color: #ffca28;
    --background: #1a1a2e;
    --card-bg: #16213e;
    --text-color: #e8e8e8;
    --text-muted: #a0a0a0;
    --border-color: #2a2a4a;
    --code-bg: #0f0f1a;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--background);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    background: var(--card-bg);
    border-radius: 12px;
    box-shadow: 0 2px 8px var(--shadow-color);
    margin-bottom: 20px;
    transition: background-color 0.3s ease;
}

.header h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
}

.header-controls {
    display: flex;
    align-items: center;
    gap: 15px;
}

.language-selector {
    display: flex;
    gap: 8px;
}

.lang-btn {
    padding: 8px 16px;
    border: 1px solid var(--border-color);
    background: var(--card-bg);
    color: var(--text-color);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.9rem;
}

.lang-btn:hover {
    background: var(--background);
}

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

/* Theme toggle button */
.theme-toggle {
    width: 44px;
    height: 44px;
    border: 1px solid var(--border-color);
    background: var(--card-bg);
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
}

.theme-toggle:hover {
    background: var(--background);
    transform: rotate(15deg);
}

/* Mode tabs */
.mode-tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.tab {
    flex: 1;
    padding: 15px 30px;
    border: none;
    background: var(--card-bg);
    color: var(--text-color);
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.2s ease;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.tab:hover {
    background: var(--background);
}

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

/* Main content */
.main-content {
    flex: 1;
    background: var(--card-bg);
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 2px 8px var(--shadow-color);
    transition: background-color 0.3s ease;
    overflow: hidden;
}

/* Buttons */
.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.2s ease;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
    background: var(--primary-dark);
}

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

.btn-secondary:hover:not(:disabled) {
    background: #5a6268;
}

.btn-small {
    padding: 8px 16px;
    font-size: 0.85rem;
}

.btn-hint {
    background: var(--warning-color);
    color: #333;
}

.btn-hint:disabled {
    background: #999;
    color: #666;
}

.controls {
    margin-bottom: 20px;
}

.controls .btn {
    width: 100%;
}

/* Keys display */
.keys-display {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin: 20px 0;
}

.key-box {
    padding: 20px;
    border-radius: 8px;
    border: 2px solid;
}

.key-box.public {
    border-color: var(--success-color);
    background: rgba(40, 167, 69, 0.1);
}

.key-box.private {
    border-color: var(--error-color);
    background: rgba(220, 53, 69, 0.1);
}

.key-box h4 {
    margin-bottom: 10px;
    color: var(--text-color);
}

/* Step cards */
.steps-container {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin: 20px 0;
}

.step-card {
    background: var(--background);
    border-radius: 8px;
    padding: 20px;
    border-left: 4px solid var(--primary-color);
    transition: background-color 0.3s ease;
    overflow-wrap: break-word;
    word-break: break-word;
}

.step-title {
    font-size: 1.1rem;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.step-content {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.step-content .label {
    font-weight: 600;
    color: var(--text-muted);
    margin-right: 8px;
}

.formula, .result, .explanation {
    padding: 8px 12px;
    background: var(--card-bg);
    border-radius: 6px;
    transition: background-color 0.3s ease;
    overflow-wrap: break-word;
    word-break: break-word;
}

code {
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    background: var(--code-bg);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.95em;
    transition: background-color 0.3s ease;
    overflow-wrap: break-word;
    word-break: break-word;
}

.result-value {
    color: var(--primary-color);
    font-weight: 600;
}

.explanation p {
    color: var(--text-muted);
    font-size: 0.95rem;
    margin-top: 5px;
}

/* Encryption section */
.encryption-section {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 2px solid var(--border-color);
}

.encryption-section h3 {
    margin-bottom: 15px;
}

.input-group {
    display: flex;
    gap: 10px;
    align-items: center;
    margin-bottom: 15px;
}

.message-input {
    flex: 1;
    max-width: 200px;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: var(--card-bg);
    color: var(--text-color);
    transition: all 0.2s ease;
}

.message-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.error {
    color: var(--error-color);
    margin: 10px 0;
}

.result-section {
    margin: 20px 0;
}

.encrypted-result, .decrypted-result {
    margin-top: 15px;
    padding: 15px;
    background: var(--background);
    border-radius: 8px;
    display: flex;
    align-items: center;
    gap: 15px;
}

.big-number {
    font-size: 1.5rem;
    color: var(--primary-color);
    font-weight: 600;
}

/* Test mode */
.test-mode .instructions {
    margin-bottom: 20px;
    color: var(--text-muted);
}

.no-problem {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
    font-size: 1.2rem;
}

.given-values {
    background: var(--background);
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 25px;
    transition: background-color 0.3s ease;
}

.given-values h3 {
    margin-bottom: 10px;
    color: var(--primary-color);
}

.given-values code {
    font-size: 1.1rem;
}

/* Stats panel - anti-cheat */
.stats-panel {
    background: linear-gradient(135deg, var(--card-bg) 0%, var(--background) 100%);
    border: 2px solid var(--primary-color);
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 25px;
    position: relative;
    overflow: hidden;
}

.stats-panel::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: repeating-linear-gradient(
        45deg,
        transparent,
        transparent 10px,
        rgba(74, 144, 217, 0.03) 10px,
        rgba(74, 144, 217, 0.03) 20px
    );
    pointer-events: none;
}

.stats-row {
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
    position: relative;
    z-index: 1;
}

.stat-item {
    text-align: center;
    padding: 10px 20px;
    background: var(--card-bg);
    border-radius: 8px;
    min-width: 120px;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.stat-item.errors {
    border-left: 4px solid var(--error-color);
}

.stat-item.hints {
    border-left: 4px solid var(--warning-color);
}

.stat-item.verification {
    border-left: 4px solid var(--success-color);
    min-width: 180px;
}

.stat-label {
    display: block;
    font-size: 0.8rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 5px;
}

.stat-value {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
}

.stat-item.errors .stat-value {
    color: var(--error-color);
}

.stat-item.hints .stat-value {
    color: var(--warning-color);
}

.verification-code {
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 1.1rem !important;
    color: var(--success-color) !important;
    letter-spacing: 1px;
}

.test-fields {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.test-field {
    padding: 15px;
    background: var(--background);
    border-radius: 8px;
    transition: background-color 0.3s ease;
}

.test-field label {
    display: block;
    font-weight: 600;
    margin-bottom: 10px;
}

.field-row {
    display: flex;
    gap: 10px;
    align-items: center;
    flex-wrap: wrap;
}

.test-input {
    width: 150px;
    padding: 10px;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
    background: var(--card-bg);
    color: var(--text-color);
    transition: all 0.2s ease;
}

.test-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.test-input.input-correct {
    border-color: var(--success-color);
    background: rgba(40, 167, 69, 0.1);
}

.test-input.input-incorrect {
    border-color: var(--error-color);
    background: rgba(220, 53, 69, 0.1);
}

.feedback {
    display: block;
    margin-top: 8px;
    font-weight: 500;
}

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

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

.hint {
    margin-top: 10px;
    padding: 10px;
    background: rgba(255, 193, 7, 0.2);
    border-radius: 6px;
    font-size: 0.9rem;
}

body.dark-theme .hint {
    background: rgba(255, 202, 40, 0.15);
}

.success-message {
    background: var(--success-color);
    color: white;
    padding: 20px;
    border-radius: 8px;
    text-align: center;
    margin-bottom: 20px;
}

.success-message p {
    margin: 5px 0;
}

.success-message p:first-child {
    font-size: 1.2rem;
    font-weight: 600;
}

.final-stats {
    font-size: 1rem;
    opacity: 0.9;
}

.verification-final {
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.95rem;
    background: rgba(255, 255, 255, 0.2);
    padding: 8px 15px;
    border-radius: 6px;
    display: inline-block;
    margin-top: 10px;
}

/* Footer */
.footer {
    text-align: center;
    padding: 20px;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 20px;
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
}

.footer a:hover {
    text-decoration: underline;
}

/* Responsive design */
/* Verify mode (for teachers) */
.verify-mode {
    max-width: 500px;
    margin: 0 auto;
}

.verify-mode .instructions {
    margin-bottom: 25px;
    color: var(--text-muted);
    text-align: center;
}

.verify-inputs {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin-bottom: 25px;
}

.verify-inputs .input-row {
    display: flex;
    align-items: center;
    gap: 15px;
}

.verify-inputs label {
    min-width: 140px;
    font-weight: 500;
}

.verify-input {
    flex: 1;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: var(--card-bg);
    color: var(--text-color);
    transition: all 0.2s ease;
}

.verify-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.verify-input.code-input {
    font-family: 'Consolas', 'Monaco', monospace;
    letter-spacing: 2px;
    text-transform: uppercase;
}

.verify-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-bottom: 25px;
}

.verify-result {
    padding: 25px;
    border-radius: 12px;
    text-align: center;
}

.verify-result h3 {
    margin-bottom: 15px;
    font-size: 1.3rem;
}

.verify-result.valid {
    background: rgba(40, 167, 69, 0.15);
    border: 2px solid var(--success-color);
}

.verify-result.valid h3 {
    color: var(--success-color);
}

.verify-result.invalid {
    background: rgba(220, 53, 69, 0.15);
    border: 2px solid var(--error-color);
}

.verify-result.invalid h3 {
    color: var(--error-color);
}

.result-details {
    text-align: left;
    max-width: 300px;
    margin: 0 auto;
}

.result-details p {
    margin: 8px 0;
    padding: 8px 12px;
    background: var(--card-bg);
    border-radius: 6px;
}

.grade-info {
    margin-top: 15px !important;
    padding: 12px !important;
    background: var(--primary-color) !important;
    color: white;
    font-weight: 500;
    text-align: center;
}

/* Responsive design */
@media (max-width: 768px) {
    .header {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }

    .header h1 {
        font-size: 1.2rem;
    }

    .header-controls {
        flex-direction: column;
        gap: 10px;
    }

    .keys-display {
        grid-template-columns: 1fr;
    }

    .mode-tabs {
        flex-direction: column;
    }

    .field-row {
        flex-direction: column;
        align-items: stretch;
    }

    .test-input {
        width: 100%;
    }

    .stats-row {
        flex-direction: column;
    }

    .stat-item {
        width: 100%;
    }

    .verify-inputs .input-row {
        flex-direction: column;
        align-items: stretch;
    }

    .verify-inputs label {
        min-width: auto;
    }

    .verify-actions {
        flex-direction: column;
    }

    .app {
        padding: 10px;
    }

    .main-content {
        padding: 15px;
    }

    .step-card {
        padding: 12px;
    }
}