diff --git a/core/src/Json.cpp b/core/src/Json.cpp
index 11c938f..a4bd20c 100644
--- a/core/src/Json.cpp
+++ b/core/src/Json.cpp
@@ -298,3 +298,173 @@ private:
         return true;
     }
 
+    bool parseEscape(std::string& out) {
+        if (atEnd()) {
+            fail("unexpected end of input after '\\'");
+            return false;
+        }
+        int escapeLine = line;
+        int escapeColumn = column;
+        char c = advance();
+        switch (c) {
+            case '"': out.push_back('"'); return true;
+            case '\\': out.push_back('\\'); return true;
+            case '/': out.push_back('/'); return true;
+            case 'b': out.push_back('\b'); return true;
+            case 'f': out.push_back('\f'); return true;
+            case 'n': out.push_back('\n'); return true;
+            case 'r': out.push_back('\r'); return true;
+            case 't': out.push_back('\t'); return true;
+            case 'u': break;
+            default:
+                failAt(escapeLine, escapeColumn,
+                       std::string("unknown escape sequence '\\") + c + "'");
+                return false;
+        }
+        uint32_t unit = 0u;
+        if (!parseHexQuad(unit)) return false;
+        if (unit >= 0xDC00u && unit <= 0xDFFFu) {
+            failAt(escapeLine, escapeColumn, "low surrogate without a preceding high surrogate");
+            return false;
+        }
+        if (unit >= 0xD800u && unit <= 0xDBFFu) {
+            if (cursor + 1u >= src.size() || src[cursor] != '\\' || src[cursor + 1u] != 'u') {
+                failAt(escapeLine, escapeColumn, "high surrogate without a following low surrogate");
+                return false;
+            }
+            advance();
+            advance();
+            uint32_t low = 0u;
+            if (!parseHexQuad(low)) return false;
+            if (low < 0xDC00u || low > 0xDFFFu) {
+                failAt(escapeLine, escapeColumn, "high surrogate followed by a non low surrogate");
+                return false;
+            }
+            uint32_t combined = 0x10000u + ((unit - 0xD800u) << 10) + (low - 0xDC00u);
+            appendUtf8(combined, out);
+            return true;
+        }
+        appendUtf8(unit, out);
+        return true;
+    }
+
+    bool parseString(std::string& out) {
+        advance();
+        out.clear();
+        for (;;) {
+            if (atEnd()) {
+                fail("unexpected end of input inside a string");
+                return false;
+            }
+            unsigned char c = static_cast<unsigned char>(peek());
+            if (c == '"') {
+                advance();
+                return true;
+            }
+            if (c == '\\') {
+                advance();
+                if (!parseEscape(out)) return false;
+                continue;
+            }
+            if (c < 0x20u) {
+                fail("raw control character in a string, escape it as \\u00" +
+                     std::string(1, "0123456789abcdef"[(c >> 4) & 0xFu]) +
+                     std::string(1, "0123456789abcdef"[c & 0xFu]));
+                return false;
+            }
+            if (c < 0x80u) {
+                out.push_back(static_cast<char>(c));
+                advance();
+                continue;
+            }
+            uint32_t codePoint = 0u;
+            std::size_t length = decodeUtf8(src, cursor, codePoint);
+            if (length == 0u) {
+                fail("malformed UTF-8 byte sequence in a string");
+                return false;
+            }
+            for (std::size_t i = 0u; i < length; ++i) out.push_back(advance());
+        }
+    }
+
+    bool parseNumber(JsonValue& out) {
+        std::size_t start = cursor;
+        int startLine = line;
+        int startColumn = column;
+        bool negative = false;
+        if (peek() == '-') {
+            negative = true;
+            advance();
+        }
+        if (atEnd()) {
+            fail("unexpected end of input inside a number");
+            return false;
+        }
+        if (peek() == '0') {
+            advance();
+            if (!atEnd() && peek() >= '0' && peek() <= '9') {
+                fail("leading zero in a number");
+                return false;
+            }
+        } else if (peek() >= '1' && peek() <= '9') {
+            while (!atEnd() && peek() >= '0' && peek() <= '9') advance();
+        } else {
+            fail("expected a digit after the sign");
+            return false;
+        }
+
+        bool fractional = false;
+        if (!atEnd() && peek() == '.') {
+            fractional = true;
+            advance();
+            if (atEnd() || peek() < '0' || peek() > '9') {
+                fail("expected a digit after the decimal point");
+                return false;
+            }
+            while (!atEnd() && peek() >= '0' && peek() <= '9') advance();
+        }
+        if (!atEnd() && (peek() == 'e' || peek() == 'E')) {
+            fractional = true;
+            advance();
+            if (!atEnd() && (peek() == '+' || peek() == '-')) advance();
+            if (atEnd() || peek() < '0' || peek() > '9') {
+                fail("expected a digit in the exponent");
+                return false;
+            }
+            while (!atEnd() && peek() >= '0' && peek() <= '9') advance();
+        }
+
+        std::string token = src.substr(start, cursor - start);
+        if (!fractional) {
+            const unsigned long long limit =
+                negative ? 9223372036854775808ull : 9223372036854775807ull;
+            unsigned long long magnitude = 0ull;
+            bool overflow = false;
+            for (char c : token) {
+                if (c == '-') continue;
+                magnitude = magnitude * 10ull + static_cast<unsigned long long>(c - '0');
+                if (magnitude > limit) {
+                    overflow = true;
+                    break;
+                }
+            }
+            if (!overflow) {
+                if (magnitude == 9223372036854775808ull) {
+                    out = JsonValue::makeInt(-9223372036854775807ll - 1ll);
+                } else {
+                    long long whole = static_cast<long long>(magnitude);
+                    out = JsonValue::makeInt(negative ? -whole : whole);
+                }
+                return true;
+            }
+        }
+        double value = std::strtod(token.c_str(), nullptr);
+        if (!std::isfinite(value)) {
+            failAt(startLine, startColumn, "number out of the representable range");
+            return false;
+        }
+        out = JsonValue::makeNumber(value);
+        return true;
+    }
+};
+