.tool-fullwidth {
    width: 100%;
    max-width: 100%;
    margin: 0;
    padding: 0;
}

/* Tool shell */
.academic-tool {
    max-width: 100%;
    margin: 0 auto;
}

.academic-tool.editor-section,
.editor-section.academic-tool {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.academic-tool .card:not(.result-card) {
    border: 1px solid var(--color-border, #e5e7eb);
    box-shadow: var(--shadow-sm, 0 1px 3px rgba(0, 0, 0, 0.06));
    border-radius: var(--radius, 12px);
    background: var(--color-surface, #fff);
}

.academic-tool .card-body {
    padding: 1.25rem 1.35rem;
}

.academic-tool .card-title {
    color: var(--color-text, #1f2937);
    font-weight: 700;
    font-size: 1.05rem;
}

.academic-tool .form-control,
.academic-tool .form-select,
.academic-tool .select-input,
.academic-tool textarea {
    border-radius: 8px;
    border: 1px solid var(--color-border, #e5e7eb);
}

.academic-tool .form-control:focus,
.academic-tool .form-select:focus,
.academic-tool textarea:focus {
    border-color: var(--color-primary, #0d9488);
    box-shadow: 0 0 0 3px rgba(13, 148, 136, 0.15);
}

.academic-tool .btn-primary {
    background: var(--color-primary, #0d9488);
    border-color: var(--color-primary, #0d9488);
}

.academic-tool .btn-primary:hover {
    background: var(--color-primary-hover, #0f766e);
    border-color: var(--color-primary-hover, #0f766e);
}

.academic-tool .alert {
    border-radius: 10px;
}

[data-theme="dark"] .academic-tool .card:not(.result-card) {
    background: var(--color-surface, #1f2937);
    border-color: var(--color-border, #374151);
}

[data-theme="dark"] .academic-tool .card-title,
[data-theme="dark"] .academic-tool .form-label,
[data-theme="dark"] .academic-tool {
    color: var(--color-text, #f9fafb);
}

[data-theme="dark"] .academic-tool .text-muted,
[data-theme="dark"] .academic-tool .form-text {
    color: var(--color-text-secondary, #9ca3af) !important;
}

[data-theme="dark"] .academic-tool .form-control,
[data-theme="dark"] .academic-tool .form-select,
[data-theme="dark"] .academic-tool textarea {
    background: #111827;
    color: var(--color-text, #f9fafb);
    border-color: var(--color-border, #374151);
}

/* --- tool: arithmetic-sequence-calculator --- */
.arithmetic-sequence-calculator {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

.card {
    border: 1px solid #dee2e6;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.card-title {
    color: #495057;
    font-weight: 600;
}

.result-box {
    background: #f8f9fa;
    border: 1px solid #dee2e6;
    border-radius: 8px;
    padding: 20px;
    margin-top: 20px;
}

.result-value {
    font-size: 1.5rem;
    font-weight: bold;
    color: #0d6efd;
    padding: 10px;
    background: #e7f3ff;
    border-radius: 5px;
    margin-top: 5px;
}

.formula-display {
    font-family: 'Courier New', monospace;
    font-size: 1.1rem;
    color: #6c757d;
    padding: 10px;
    background: #f8f9fa;
    border-radius: 5px;
    margin-top: 5px;
}

.calculation-steps {
    background: #fff;
    border: 1px solid #dee2e6;
    border-radius: 5px;
    padding: 15px;
    margin-top: 15px;
}

.calculation-steps h6 {
    color: #495057;
    margin-bottom: 10px;
}

.calculation-steps p {
    margin-bottom: 8px;
    color: #6c757d;
}

.sequence-display {
    font-family: 'Courier New', monospace;
    font-size: 1.1rem;
    color: #495057;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 5px;
    margin-top: 5px;
    white-space: pre-wrap;
    word-break: break-all;
}

.form-control:focus {
    border-color: #0d6efd;
    box-shadow: 0 0 0 0.2rem rgba(13, 110, 253, 0.25);
}

.btn-primary {
    background-color: #0d6efd;
    border-color: #0d6efd;
}

.btn-primary:hover {
    background-color: #0b5ed7;
    border-color: #0a58ca;
}

.nav-tabs .nav-link {
    color: #6c757d;
}

.nav-tabs .nav-link.active {
    color: #0d6efd;
    border-color: #0d6efd;
}