:root {
    --color-primary: #3d3d3d;
    --color-primary-hover: #2a2a2a;
    --color-primary-light: rgba(217, 119, 87, 0.12);
    --color-primary-shadow: rgba(45, 45, 45, 0.06);
    --color-success: #6f8f72;
    --color-error: #b85c4a;
    --color-warning: #c69245;

    --color-bg: #fcfaf8;
    --color-bg-alt: #f5f2eb;
    --color-surface: #ffffff;
    --color-surface-alt: #fdfdfc;
    --color-border: #e5e5e5;
    --color-border-hover: #d6d0c8;

    --color-text-main: #2d2d2d;
    --color-text-secondary: #6b6b6b;
    --color-text-light: #999999;
    --color-text-inverse: #ffffff;

    --color-input-bg: #fdfdfc;
    --color-disabled: #eeeae3;

    --font-heading: "Merriweather", "Songti SC", "STSong", "SimSun", "Georgia", "Times New Roman", serif;
    --font-sans: "Inter", "Söhne", -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
    --font-mono: "SF Mono", "Monaco", "Consolas", "Liberation Mono", monospace;

    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-3xl: clamp(1.875rem, 4vw, 2.25rem);

    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 600;

    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.25rem;
    --spacing-xl: 1.5rem;
    --spacing-2xl: 2.25rem;
    --spacing-3xl: 3rem;

    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-full: 9999px;

    --shadow-md: 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 4px 8px rgba(0, 0, 0, 0.08);

    --transition-base: 200ms ease;

    --container-max-width: 1200px;
    --panel-min-height: 560px;
    --textarea-min-height: 200px;
    --textarea-default-height: 330px;
    --header-height: 3.25rem;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

html {
    min-height: 100%;
    background: var(--color-bg);
}

body {
    min-height: 100vh;
    margin: 0;
    font-family: var(--font-sans);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text-main);
    background: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1,
h2 {
    margin: 0;
    font-family: var(--font-heading);
    font-weight: var(--font-weight-semibold);
    line-height: 1.35;
}

p {
    margin: 0;
}

button {
    font-family: inherit;
    cursor: pointer;
}

button:focus-visible,
.textarea:focus-visible,
.result-list__copy:focus-visible,
.tabs__btn:focus-visible {
    outline: none;
    box-shadow: 0 0 0 3px rgba(45, 45, 45, 0.06);
}

.container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-xl);
}

.header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.header__title {
    font-size: var(--font-size-3xl);
    letter-spacing: -0.03em;
    margin-bottom: var(--spacing-sm);
}

.header__subtitle {
    max-width: 65ch;
    margin: 0 auto;
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
}

.main-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-xl);
    align-items: start;
}

.panel {
    background: rgba(255, 255, 255, 0.86);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    min-height: var(--panel-min-height);
    backdrop-filter: blur(10px);
}

.panel__header {
    padding: 0.875rem var(--spacing-xl);
    border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;
}

.panel__title {
    font-size: var(--font-size-lg);
}

.panel__body {
    padding: var(--spacing-lg) var(--spacing-xl) var(--spacing-md);
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    min-height: 0;
}

.panel__actions {
    display: flex;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-xl) var(--spacing-lg);
    flex-shrink: 0;
    align-items: center;
}

.panel__actions--input {
    flex-wrap: wrap;
}

.actions__spacer {
    flex-grow: 1;
}

.textarea {
    width: 100%;
    flex-grow: 1;
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    line-height: 1.7;
    color: var(--color-text-main);
    background-color: var(--color-input-bg);
    resize: vertical;
    overflow-y: auto;
    min-height: var(--textarea-min-height);
    height: var(--textarea-default-height);
    transition: border-color var(--transition-base), box-shadow var(--transition-base), background-color var(--transition-base);
}

.textarea::placeholder {
    color: var(--color-text-light);
}

.textarea:focus {
    outline: none;
    border-color: var(--color-text-secondary);
    box-shadow: 0 0 0 3px rgba(45, 45, 45, 0.05);
    background-color: var(--color-surface);
}

.textarea--output {
    resize: none;
}

.result-list {
    position: relative;
}

.result-list__placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--color-text-light);
    text-align: center;
}

.result-list__icon {
    margin-bottom: var(--spacing-lg);
    opacity: 0.28;
}

.result-list__item {
    background-color: var(--color-surface);
    padding: 0.875rem var(--spacing-md);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    line-height: 1.6;
    border: 1px solid var(--color-border);
    transition: border-color var(--transition-base), background-color var(--transition-base);
}

.result-list__item:hover {
    border-color: var(--color-border-hover);
    background-color: var(--color-surface-alt);
}

.result-list__item:last-child {
    margin-bottom: 0;
}

.result-list__text {
    word-break: break-all;
    padding-right: var(--spacing-md);
    flex-grow: 1;
}

.result-list__copy {
    background: transparent;
    border: none;
    padding: 0.25rem;
    border-radius: var(--radius-full);
    color: var(--color-text-light);
    transition: color var(--transition-base), background-color var(--transition-base);
    flex-shrink: 0;
}

.result-list__copy:hover {
    color: #8f513d;
    background-color: var(--color-primary-light);
}

.result-list__copy--copied {
    color: var(--color-success);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: 0.625rem 1.25rem;
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    transition: background-color var(--transition-base), border-color var(--transition-base), color var(--transition-base), transform var(--transition-base), box-shadow var(--transition-base);
}

.btn__icon {
    flex-shrink: 0;
}

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

.btn--primary:hover:not(:disabled) {
    background-color: var(--color-primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

.btn--secondary {
    background-color: transparent;
    color: var(--color-primary);
    border-color: var(--color-primary);
}

.btn--secondary:hover:not(:disabled) {
    background-color: rgba(45, 45, 45, 0.04);
}

.btn--option {
    background-color: transparent;
    color: var(--color-text-secondary);
    border-color: var(--color-border);
}

.btn--option:not([aria-pressed="true"]):hover:not(:disabled) {
    color: var(--color-text-main);
    border-color: var(--color-border-hover);
    background-color: rgba(45, 45, 45, 0.03);
}

.btn--option[aria-pressed="true"] {
    background-color: var(--color-primary-light);
    border-color: #d97757;
    color: #8f513d;
    font-weight: var(--font-weight-semibold);
}

.btn--option[aria-pressed="true"]:hover:not(:disabled) {
    background-color: rgba(217, 119, 87, 0.18);
}

.btn:disabled {
    opacity: 1;
    cursor: not-allowed;
    background-color: var(--color-disabled);
    color: var(--color-text-light);
    border-color: transparent;
    box-shadow: none;
}

.tabs {
    display: flex;
    padding: 0 var(--spacing-xl);
    border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;
    height: var(--header-height);
    align-items: center;
}

.tabs__btn {
    background: none;
    border: none;
    padding: var(--spacing-lg) 0;
    margin-right: var(--spacing-xl);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-secondary);
    border-bottom: 2px solid transparent;
    transition: color var(--transition-base), border-color var(--transition-base);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.tabs__btn:hover {
    color: var(--color-text-main);
}

.tabs__btn--active {
    color: #8f513d;
    border-bottom-color: #d97757;
}

.tabs__count {
    font-size: 0.875rem;
    padding: 0.2rem 0.5rem;
    border-radius: var(--radius-full);
    background-color: var(--color-bg-alt);
    color: var(--color-text-secondary);
}

.tabs__btn--active .tabs__count {
    background-color: var(--color-primary-light);
    color: #8f513d;
}

.tab-content {
    display: none;
}

.tab-content--active {
    display: flex;
    flex-direction: column;
    flex-grow: 1;
    min-height: 0;
}

.spinner {
    display: flex;
    align-items: center;
    justify-content: center;
}

.spinner__circle {
    width: 1rem;
    height: 1rem;
    border: 2px solid rgba(255, 255, 255, 0.35);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

.toast-container {
    position: fixed;
    top: var(--spacing-xl);
    right: var(--spacing-xl);
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.toast {
    padding: var(--spacing-md) var(--spacing-lg);
    background: rgba(255, 255, 255, 0.94);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    min-width: 200px;
    max-width: 420px;
    cursor: pointer;
    animation: slideIn 300ms ease;
    backdrop-filter: blur(10px);
}

.toast span {
    overflow-wrap: anywhere;
}

.toast--success {
    border-left: 4px solid var(--color-success);
}

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

.toast--info {
    border-left: 4px solid #d97757;
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

@keyframes slideOut {
    from {
        transform: translateX(0);
        opacity: 1;
    }
    to {
        transform: translateX(100%);
        opacity: 0;
    }
}

.footer {
    text-align: center;
    margin-top: var(--spacing-2xl);
    font-size: 0.875rem;
    color: var(--color-text-light);
}

@media (max-width: 1024px) {
    .container {
        padding: var(--spacing-2xl) var(--spacing-lg);
    }

    .main-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-xl);
    }

    .panel {
        min-height: auto;
    }

    .textarea {
        min-height: 250px;
        height: 300px;
    }

    .header__title {
        font-size: 1.75rem;
    }
}

@media (max-width: 640px) {
    .container {
        padding: var(--spacing-xl) var(--spacing-md);
    }

    .header {
        margin-bottom: var(--spacing-xl);
    }

    .header__title {
        font-size: 1.5rem;
    }

    .header__subtitle {
        font-size: var(--font-size-base);
    }

    .panel__header,
    .panel__body,
    .panel__actions,
    .tabs {
        padding-left: var(--spacing-md);
        padding-right: var(--spacing-md);
    }

    .btn {
        flex-grow: 1;
    }

    .actions__spacer {
        display: none;
    }

    #convertBtn {
        width: 100%;
        order: 10;
    }

    .toast-container {
        right: var(--spacing-md);
        left: var(--spacing-md);
    }

    .toast {
        max-width: none;
    }
}