:root {
    --brand-green: #01894d;
    --brand-orange: #f39800;
    --bg-color: #f8fafb;
    --card-bg: #ffffff;
    --text-main: #333333;
    --text-sub: #666666;
    --border-color: #e5e7eb;
    --accent-color: #f0fdf4;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --radius: 12px;
}

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

body {
    font-family: 'Noto Sans JP', 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
}

/* Header */
.main-header {
    background-color: var(--brand-green);
    border-bottom: 2px solid var(--brand-orange);
    padding: 12px 0;
    color: #fff;
    position: sticky;
    top: 0;
    z-index: 100;
}

.main-header-inner {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-area {
    display: flex;
    align-items: center;
    gap: 12px;
}

.title-icon {
    width: 28px;
    height: 28px;
}

.brand-logo {
    font-size: 1.25rem;
    font-weight: 700;
}

.btn-home {
    color: #fff;
    text-decoration: none;
    font-weight: 600;
    padding: 6px 12px;
    border-radius: 6px;
    transition: background 0.2s;
}

.btn-home:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.container {
    max-width: 800px;
    margin: 30px auto;
    padding: 0 20px;
}

/* Info Section */
.info-section {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    margin-bottom: 24px;
    overflow: hidden;
}

.info-header {
    padding: 16px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    background: #fcfcfc;
}

.info-header h2 {
    font-size: 1.1rem;
    color: var(--brand-green);
    display: flex;
    align-items: center;
    gap: 8px;
}

.toggle-icon {
    width: 20px;
    height: 20px;
    transition: transform 0.3s;
}

.info-section.collapsed .toggle-icon {
    transform: rotate(-180deg);
}

.info-content {
    padding: 24px;
    border-top: 1px solid var(--border-color);
}

.info-section.collapsed .info-content {
    display: none;
}

.usage-steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-top: 15px;
}

.usage-step {
    padding-left: 35px;
    position: relative;
    font-size: 0.9rem;
}

.usage-step::before {
    content: attr(data-step);
    position: absolute;
    left: 0;
    top: 0;
    width: 24px;
    height: 24px;
    background: var(--brand-green);
    color: #fff;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-weight: bold;
}

/* Tabs */
.tab-container {
    display: flex;
    gap: 8px;
    margin-bottom: 0px;
    padding: 0 10px;
}

.tab-btn {
    padding: 12px 24px;
    border: 1px solid var(--border-color);
    border-bottom: none;
    background: #eef2f5;
    border-radius: 10px 10px 0 0;
    cursor: pointer;
    font-weight: 600;
    color: var(--text-sub);
    transition: all 0.2s;
}

.tab-btn.active {
    background: #fff;
    color: var(--brand-green);
    border-bottom: 2px solid #fff;
    margin-bottom: -1px;
    z-index: 2;
}

/* Cards */
.card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 30px;
    margin-bottom: 24px;
    box-shadow: var(--shadow);
}

.hidden {
    display: none !important;
}

/* Calc Form */
.ratio-inputs {
    display: flex;
    align-items: center;
    gap: 24px;
    flex-wrap: wrap;
}

.input-group {
    flex: 1;
    min-width: 250px;
}

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-sub);
}

.dual-input {
    display: flex;
    align-items: center;
    gap: 10px;
}

.input-field {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1.1rem;
    outline: none;
    transition: border-color 0.2s;
}

.input-field:focus {
    border-color: var(--brand-green);
}

.separator {
    font-weight: bold;
    font-size: 1.2rem;
    color: var(--text-sub);
}

.arrow-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--brand-orange);
    width: 32px;
    height: 32px;
}

.preset-group {
    margin-top: 12px;
}

.select-field {
    width: 100%;
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background-color: #fcfcfc;
    cursor: pointer;
}

.input-hint {
    font-size: 0.8rem;
    color: var(--text-sub);
    margin-top: 8px;
}

/* Polynomial Grid */
.poly-container {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.poly-header {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 20px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-sub);
    padding-right: 48px;
}

.poly-row {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 20px;
    align-items: center;
}

.btn-remove {
    background: none;
    border: none;
    color: #ef4444;
    cursor: pointer;
    font-size: 1.5rem;
    line-height: 1;
    padding: 4px;
    display: flex;
    align-items: center;
}

.poly-actions {
    margin-top: 10px;
}

/* Options */
.options-container {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.option-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
}

.option-item label {
    display: block;
    font-size: 0.85rem;
    margin-bottom: 6px;
    font-weight: 600;
}

/* Result Box */
.result-box {
    margin-top: 24px;
    background: var(--accent-color);
    border: 1px solid #d1fae5;
    border-radius: 8px;
    padding: 16px;
}

.result-title {
    font-size: 0.85rem;
    font-weight: 700;
    color: var(--brand-green);
    margin-bottom: 4px;
}

.result-text {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--brand-green);
    letter-spacing: 0.05em;
}

/* Actions */
.calc-actions {
    margin-top: 30px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.calculate-btn {
    width: 100%;
    background: var(--brand-green);
    color: #fff;
    border: none;
    padding: 16px;
    font-size: 1.1rem;
    font-weight: 700;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.calculate-btn:hover {
    background: var(--brand-orange);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(243, 152, 0, 0.2);
}

.sub-actions {
    display: flex;
    gap: 10px;
}

.sub-actions .secondary-btn {
    flex: 1;
}

.secondary-btn {
    background: #fff;
    color: var(--text-main);
    border: 1px solid var(--border-color);
    padding: 10px 20px;
    font-size: 0.95rem;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.secondary-btn:hover {
    border-color: var(--brand-green);
    color: var(--brand-green);
    background: var(--accent-color);
}

.small-btn {
    padding: 6px 12px;
    font-size: 0.85rem;
}

/* History */
.history-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
    max-height: 400px;
    overflow-y: auto;
}

.history-item {
    background: #fbfbfb;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.history-info {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.history-ratio {
    font-weight: 700;
    color: var(--text-main);
}

.history-date {
    font-size: 0.75rem;
    color: var(--text-sub);
}

.history-item-actions {
    display: flex;
    gap: 8px;
}

.empty-msg {
    text-align: center;
    color: var(--text-sub);
    padding: 20px;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(0, 0, 0, 0.8);
    color: #fff;
    padding: 10px 24px;
    border-radius: 30px;
    font-size: 0.9rem;
    opacity: 0;
    transition: opacity 0.3s;
    pointer-events: none;
    z-index: 1000;
}

.toast.show {
    opacity: 1;
}

@media (max-width: 600px) {
    .container {
        padding: 0 15px;
    }

    .ratio-inputs {
        flex-direction: column;
        align-items: stretch;
    }

    .arrow-icon {
        transform: rotate(90deg);
        margin: 10px 0;
    }
}