:root {
    --primary: #6366F1;
    --primary-hover: #4F46E5;
    --bg: #FAFAFA;
    --surface: #FFFFFF;
    --text-primary: #0A0A0A;
    --text-secondary: #6B6B6B;
    --border: #E8E8EC;
    --success: #10B981;
    --error: #EF4444;
    
    --font-display: 'General Sans', sans-serif;
    --font-body: 'DM Sans', sans-serif;
    --font-code: 'JetBrains Mono', monospace;
}

body {
    margin: 0;
    padding: 0;
    background-color: var(--bg);
    color: var(--text-primary);
    font-family: var(--font-body);
    -webkit-font-smoothing: antialiased;
    font-size: 13px;
}

h1, h2, h3 {
    font-family: var(--font-display);
    font-weight: 700;
    letter-spacing: -0.03em;
    margin: 0;
}

h1 { font-size: 28px; }
h2 { font-size: 18px; margin-bottom: 12px; }
h3 { font-size: 15px; margin-bottom: 2px; }
p { line-height: 1.4; margin: 4px 0; }
.subhead { font-size: 14px; color: var(--text-secondary); margin-bottom: 0; }
.text-secondary { color: var(--text-secondary); font-size: 12px; }

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 16px 24px;
}

header { margin-bottom: 20px; }

.grid-layout {
    display: grid;
    grid-template-columns: 1fr 1.3fr; /* Slightly more room for math in log */
    gap: 20px;
    align-items: start;
}

/* Cards */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.02);
}

/* Controls */
.section-divider {
    border-top: 1px solid var(--border);
    padding-top: 12px;
    margin-top: 12px;
}
.section-divider:first-of-type { border-top: none; margin-top: 0; padding-top: 0; }

.action-row {
    display: flex;
    gap: 8px;
    margin-top: 8px;
}

input[type="text"], input[type="number"] {
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 6px 10px;
    font-family: var(--font-code);
    font-size: 13px;
    flex: 1;
    background: var(--surface);
}
input:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 2px rgba(99,102,241,0.12); }

/* Buttons */
.btn {
    border: none;
    border-radius: 6px;
    padding: 6px 14px;
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 13px;
    cursor: pointer;
    white-space: nowrap;
}
.btn-primary { background-color: var(--primary); color: white; }
.btn-primary:hover:not(:disabled) { background-color: var(--primary-hover); }
.btn-secondary { background-color: transparent; border: 1px solid var(--border); color: var(--text-primary); }
.btn-secondary:hover:not(:disabled) { border-color: var(--text-secondary); background-color: var(--bg); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.w-full { width: 100%; margin-top: 8px; }

/* States */
.disabled-overlay { opacity: 0.4; pointer-events: none; }
.disabled-overlay.active { opacity: 1; pointer-events: auto; }

/* Log and Visualization */
.log-container {
    font-family: var(--font-code);
    font-size: 12px;
    background: var(--bg);
    padding: 12px;
    border-radius: 6px;
    border: 1px solid var(--border);
}

.log-entry { margin-bottom: 12px; border-bottom: 1px solid var(--border); padding-bottom: 12px; }
.log-entry:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }
.log-title { font-family: var(--font-display); font-weight: 700; color: var(--primary); margin-bottom: 4px; font-size: 14px; }
.log-data { color: var(--text-secondary); line-height: 1.4; }

/* Calculation Box (Educational) */
.calc-box {
    background: rgba(0,0,0,0.03);
    border-left: 2px solid var(--border);
    padding: 6px 10px;
    margin: 6px 0;
    font-size: 11px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4px 12px;
    color: var(--text-primary);
}

/* Bit Chips */
.bits-display { display: flex; gap: 4px; margin: 6px 0; flex-wrap: wrap; }
.bit-chip {
    display: inline-flex; flex-direction: column; align-items: center;
    background: #E8E8EC; color: var(--text-primary);
    border-radius: 4px; padding: 4px 8px; font-weight: 700; font-size: 14px; min-width: 16px;
}
.bit-label { font-size: 9px; color: var(--text-secondary); font-weight: 400; margin-top: 2px; }
.bit-parity { background-color: rgba(99,102,241,0.1); color: var(--primary); }
.bit-error { background-color: rgba(239,68,68,0.1); color: var(--error); border: 1px solid var(--error); }
.bit-corrected { background-color: rgba(16,185,129,0.1); color: var(--success); border: 1px solid var(--success); }