:root {
    --paper-ink: #263446;
    --paper-muted: #718096;
    --paper-accent: #315d78;
    --paper-accent-soft: #edf5f7;
    --paper-line: #dce5e9;
    --paper-code: #17212b;
    --paper-code-text: #e7eef3;
    --paper-highlight: #fff0a8;
}

.proof-text-card {
    position: relative;
}

.proof-text-card > .proof-text-flip-button {
    display: flex;
    width: fit-content;
    margin: 0 0 4px auto;
}

.proof-text-flip-inner {
    width: 100%;
}

.proof-text {
    color: var(--paper-ink);
    font-family: Georgia, "Noto Serif SC", "Songti SC", serif;
    font-size: 16px;
    line-height: 1.8;
}

.proof-text > :first-child {
    margin-top: 0;
}

.proof-text > :last-child {
    margin-bottom: 0;
}

.proof-text h1,
.proof-text h2,
.proof-text h3,
.proof-text h4 {
    display: block;
    position: relative;
    color: #172b3a;
    border: 0;
    font-family: ui-serif, Georgia, "Noto Serif SC", serif;
    line-height: 1.3;
    letter-spacing: -0.015em;
    scroll-margin-top: 28px;
}

.proof-text h1 {
    margin: 64px 0 24px;
    padding: 0;
    font-size: 34px;
}

.proof-text h2 {
    margin: 48px 0 20px;
    padding: 0;
    font-size: 27px;
}

.proof-text h3 {
    margin: 36px 0 16px;
    font-size: 21px;
}

.proof-text h4 {
    margin: 28px 0 12px;
    font-size: 17px;
}

.proof-text p {
    margin: 0 0 18px;
}

.proof-text strong {
    color: #132b3a;
    font-weight: 750;
}

.proof-text em {
    color: #40586a;
}

.proof-text s {
    color: var(--paper-muted);
    text-decoration-thickness: 1px;
}

.proof-text u {
    text-decoration-color: var(--paper-accent);
    text-decoration-thickness: 1px;
    text-underline-offset: 4px;
}

.proof-text mark {
    margin: 0 1px;
    padding: 1px 4px;
    border-radius: 3px;
    background: linear-gradient(transparent 18%, var(--paper-highlight) 18%, var(--paper-highlight) 88%, transparent 88%);
    color: inherit;
}

.proof-text sup,
.proof-text sub {
    color: var(--paper-accent);
    font-size: 0.72em;
    font-weight: 650;
}

.proof-text a {
    color: var(--paper-accent);
    text-decoration-color: #9bb7c5;
    text-decoration-thickness: 1px;
    text-underline-offset: 3px;
    transition: color 0.2s ease, text-decoration-color 0.2s ease;
}

.proof-text a:hover {
    color: #1f455d;
    text-decoration-color: currentColor;
}

.proof-text code:not(.katex *) {
    padding: 2px 6px;
    border: 1px solid #dbe6eb;
    border-radius: 5px;
    background: #f3f7f8;
    color: #9f3a38;
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 0.86em;
}

.proof-text .page-code {
    position: relative;
    margin: 24px 0;
    padding: 20px 22px;
    border: 1px solid #273746;
    border-radius: 10px;
    background: var(--paper-code);
    box-shadow: 0 12px 32px -24px rgba(15, 23, 42, 0.7);
    color: var(--paper-code-text);
    line-height: 1.65;
}

.proof-text .page-code code {
    padding: 0;
    border: 0;
    background: transparent;
    color: inherit;
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 13px;
}

.proof-text .code-theme-dark.code-comment { color: #7f8f9a; font-style: italic; }
.proof-text .code-theme-dark.code-keyword { color: #ff7b72; }
.proof-text .code-theme-dark.code-type,
.proof-text .code-theme-dark.code-function { color: #d2a8ff; }
.proof-text .code-theme-dark.code-builtin,
.proof-text .code-theme-dark.code-constant,
.proof-text .code-theme-dark.code-number { color: #79c0ff; }
.proof-text .code-theme-dark.code-namespace,
.proof-text .code-theme-dark.code-tag,
.proof-text .code-theme-dark.code-inserted { color: #7ee787; }
.proof-text .code-theme-dark.code-attribute,
.proof-text .code-theme-dark.code-heading,
.proof-text .code-theme-dark.code-strong { color: #ffa657; }
.proof-text .code-theme-dark.code-string { color: #a5d6ff; }
.proof-text .code-theme-dark.code-operator,
.proof-text .code-theme-dark.code-punctuation { color: #c9d1d9; }
.proof-text .code-theme-dark.code-emphasis { font-style: italic; }
.proof-text .code-theme-dark.code-deleted,
.proof-text .code-theme-dark.code-error { color: #ff7b72; }

.proof-text .code-comment {
    color: #7f8f9a;
    font-style: italic;
}

.proof-text .code-keyword {
    color: #ff7b72;
}

.proof-text .code-type,
.proof-text .code-class {
    color: #d2a8ff;
}

.proof-text .code-builtin,
.proof-text .code-constant {
    color: #79c0ff;
}

.proof-text .code-function {
    color: #d2a8ff;
}

.proof-text .code-namespace,
.proof-text .code-tag {
    color: #7ee787;
}

.proof-text .code-attribute {
    color: #ffa657;
}

.proof-text .code-string {
    color: #a5d6ff;
}

.proof-text .code-number {
    color: #79c0ff;
}

.proof-text .code-operator,
.proof-text .code-punctuation {
    color: #c9d1d9;
}

.proof-text .code-heading,
.proof-text .code-strong {
    color: #ffa657;
    font-weight: 700;
}

.proof-text .code-emphasis {
    font-style: italic;
}

.proof-text .code-inserted {
    color: #7ee787;
}

.proof-text .code-deleted,
.proof-text .code-error {
    color: #ff7b72;
}

.proof-text ul,
.proof-text ol {
    margin: 20px 0 24px;
    padding-left: 0;
}

.proof-text ul {
    list-style: none;
}

.proof-text ol {
    padding-left: 34px;
}

.proof-text li {
    position: relative;
    margin: 10px 0;
    padding-left: 36px;
}

.proof-text li > p {
    margin: 0;
}

.proof-text ul > li::before {
    content: "•";
    position: absolute;
    top: 0;
    left: 9px;
    color: var(--paper-accent);
    font-size: 1em;
    line-height: inherit;
}

.proof-text ol > li {
    padding-left: 8px;
}

.proof-text ol > li::marker {
    color: var(--paper-accent);
    font-family: ui-monospace, monospace;
    font-size: 0.85em;
    font-weight: 750;
}

.proof-text blockquote {
    position: relative;
    margin: 26px 0;
    padding: 18px 22px 18px 54px;
    border: 0;
    border-radius: 10px;
    background: #f5f8f9;
    color: #4a6170;
}

.proof-text blockquote::before {
    content: "“";
    position: absolute;
    top: 2px;
    left: 18px;
    color: #a2bdca;
    font-family: Georgia, serif;
    font-size: 52px;
    line-height: 1;
}

.proof-text blockquote p:last-child {
    margin-bottom: 0;
}

.proof-text .display-math {
    margin: 26px 0;
    padding: 0;
    overflow-x: auto;
    text-align: center;
}

.proof-text ::selection {
    background: #cfe4ec;
}

@media (max-width: 767px) {
    .proof-text {
        font-size: 15px;
    }

    .proof-text h1 {
        margin-top: 42px;
        font-size: 28px;
    }

    .proof-text h2 {
        font-size: 23px;
    }
}