* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: system-ui, -apple-system, sans-serif;
    line-height: 1.5;
    color: #000;
    background: #fff;
    padding: 1rem;
}

main {
    max-width: 800px;
    margin: 0 auto;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

h1 {
    font-size: 1.5rem;
    margin-bottom: 0;
}

.back-link {
    color: #000;
    text-decoration: none;
    font-size: 0.9rem;
}

.back-link:hover {
    text-decoration: underline;
}

#config {
    margin-bottom: 1rem;
}

fieldset {
    border: 1px solid #000;
    padding: 0.75rem 1rem;
    margin-bottom: 0.75rem;
    position: relative;
}

legend {
    font-weight: bold;
    padding: 0 0.5rem;
}

.collapse-toggle {
    position: absolute;
    top: -1.5rem;
    right: 0.5rem;
    width: 1.5rem;
    height: 1.5rem;
    padding: 0;
    font-size: 1rem;
    line-height: 1;
    border: 1px solid #000;
    background: #fff;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}

.collapse-toggle:hover {
    background: #f0f0f0;
}

.fieldset-content {
    display: block;
}

fieldset.collapsed .fieldset-content {
    display: none;
}

fieldset.rule-disabled .fieldset-content {
    opacity: 0.5;
}

fieldset.rule-disabled .fieldset-content input,
fieldset.rule-disabled .fieldset-content select {
    pointer-events: none;
}

.fieldset-row {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 0.5rem;
}

.fieldset-row:last-child {
    margin-bottom: 0;
}

.field-label {
    min-width: 5.5rem;
    font-weight: normal;
}

fieldset label {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
    min-width: 5rem;
    cursor: pointer;
}

select,
input[type="number"] {
    padding: 0.25rem 0.5rem;
    font-size: 1rem;
    border: 1px solid #000;
    background: #fff;
}

input[type="number"] {
    width: 5rem;
}

.controls {
    margin-top: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

button {
    padding: 0.5rem 1rem;
    font-size: 1rem;
    border: 1px solid #000;
    background: #fff;
    cursor: pointer;
}

button:hover {
    background: #f0f0f0;
}

hr {
    border: none;
    border-top: 1px solid #000;
    margin: 1rem 0;
}

/* Exercise 1: Partner Pairs */
#equations {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.5rem 2rem;
    margin-bottom: 2rem;
}

.equation {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 1.25rem;
    font-family: monospace;
    padding: 0.25rem 0;
}

.equation-number {
    width: 4.5ch;
    text-align: right;
    color: #666;
}

.equation-text {
    flex: 1;
}

.equation .num {
    display: inline-block;
    width: 3ch;
}

.equation .num.align-center {
    text-align: center;
}

.equation .num.align-left {
    text-align: left;
}

.equation .blank {
    display: inline-block;
    width: 3ch;
    border-bottom: 2px solid #000;
    text-align: center;
}

/* Exercise 2: Partner Sequences */
#sequences {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem 2rem;
}

.sequence-box {
    border: 2px solid #000;
    padding: 1.5rem;
    break-inside: avoid;
    background: #fff;
    max-width: 300px;
    margin: 0 auto;
    position: relative;
}

.sequence-regenerate {
    position: absolute;
    top: 0.25rem;
    right: 0.25rem;
    padding: 0.125rem 0.5rem;
    font-size: 0.75rem;
    border: 1px solid #000;
    background: #fff;
    cursor: pointer;
}

.sequence-regenerate:hover {
    background: #f0f0f0;
}

.sequence-item {
    font-family: monospace;
    font-size: 1.1rem;
    margin: 0.25rem 0;
    text-align: center;
}

.sequence-item .num {
    display: inline-block;
    width: 3ch;
}

.sequence-item .num.align-center {
    text-align: center;
}

.sequence-item .num.align-left {
    text-align: left;
}

.sequence-item .blank {
    display: inline-block;
    width: 3ch;
    border-bottom: 2px solid #000;
    text-align: center;
}

.print-only {
    display: none;
}

#summaryContent ul {
    padding-left: 0.5rem;
    list-style-position: inside;
}

/* Print styles */
@media print {
    body {
        padding: 0;
        font-size: 12pt;
    }

    h1 {
        font-size: 14pt;
        margin-bottom: 0.5rem;
    }

    .back-link {
        display: none;
    }

    fieldset,
    .controls {
        display: none;
    }

    .print-only {
        display: block;
        font-size: 10pt;
        color: #666;
        margin-bottom: 1rem;
    }

    hr {
        margin: 0.5rem 0;
    }

    #equations {
        gap: 0.25rem 1.5rem;
        margin-bottom: 1.5rem;
    }

    .equation {
        font-size: 14pt;
        padding: 0.15rem 0;
    }

    .equation-number {
        width: 4.5ch;
    }

    .equation .num {
        width: 3ch;
    }

    .equation .blank {
        width: 3ch;
    }

    #sequences {
        gap: 1rem 1.5rem;
    }

    .sequence-box {
        border: 2px solid #000;
        padding: 1.5rem;
        max-width: 300px;
        margin: 0 auto;
    }

    .sequence-regenerate {
        display: none;
    }

    .sequence-item {
        font-size: 12pt;
        margin: 0.2rem 0;
    }

    .sequence-item .num {
        width: 3ch;
    }

    .sequence-item .blank {
        width: 3ch;
    }
}