:root {
    --bg-color: #FFFFFF;
    --text-color: #1F1D21;
    --text-muted: #555555;
    --primary-color: #BC0031;
    /* Green-500 */
    --primary-hover: #7E0021;
    --secondary-color: #555555;
    /* Gray-500 */
    --secondary-hover: #1F1D21;
    --card-bg: #ffffff;
    --code-bg: #F9F9F9;
    /* Gray-900 */
    --code-text: #1F1D21;
    /* Green-400 */
    --highlight-bg: #FBEEF1;
    /* Green-200 */

    /* Language Colors */
    --lang-assembly: #1F1D21;
    /* Red-500 */
    --lang-python: #BC0031;
    /* Blue-500 */
    --lang-javascript: #5B7BA8;
    /* Yellow-500 */
    --lang-cpp: #7E0021;
    /* Purple-500 */
}

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

body {
    font-family: "Source Sans 3", "Source Sans Pro", Arial, Helvetica, sans-serif;
    border-top: 6px solid #BC0031;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
}

.app-container {
    max-width: 1400px;
    /* 6xl */
    margin: 0 auto;
    padding: 2rem;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 1.875rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-muted);
    font-family: Faustina, Georgia, serif;
    font-style: italic;
}

/* Tabs */
.tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
    margin-bottom: 1.5rem;
}

.tab-btn {
    padding: 0.5rem 1.5rem;
    border: none;
    border-radius: 0.5rem 0.5rem 0 0;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    background-color: #e5e7eb;
    color: var(--text-muted);
}

.tab-btn:hover {
    background-color: #d1d5db;
}

.tab-btn.active {
    color: white;
}

/* Code Card */
.code-card {
    background-color: var(--card-bg);
    border-radius: 0.5rem;
    border: 1px solid #BEC6D1;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.code-content {
    background-color: var(--code-bg);
    color: var(--code-text);
    border-radius: 0;
    border: 1px solid #BEC6D1;
    overflow: hidden;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.875rem;
}

.code-header {
    background-color: #1F1D21;
    color: white;
    padding: 0.5rem 1rem;
    font-weight: 600;
}

.code-lines {
    padding: 0.5rem 0;
}

.code-line {
    padding: 0.25rem 1rem;
    transition: background-color 0.3s;
    white-space: pre;
}

.code-line.active {
    background-color: var(--highlight-bg);
    color: #7E0021;
    box-shadow: inset 3px 0 0 #BC0031;
}

.code-explanation {
    margin-top: 1rem;
    padding: 1rem;
    background-color: #F9F9F9;
    border-left: 3px solid #BC0031;
    border-radius: 0.5rem;
    color: var(--text-muted);
}

/* Controls */
.controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 1.5rem;
}

.btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 0.5rem;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    color: white;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.btn:disabled {
    background-color: #BEC6D1;
    cursor: not-allowed;
    box-shadow: none;
}

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

.btn.primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

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

.btn.secondary:hover {
    background-color: var(--secondary-hover);
}

/* Iteration Display */
.iteration-card {
    background-color: var(--card-bg);
    border-radius: 0.5rem;
    border: 1px solid #BEC6D1;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    text-align: center;
}

.iteration-card h3 {
    margin-bottom: 1rem;
}

.iteration-circles {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
    align-items: center;
}

.circle {
    width: 4rem;
    height: 4rem;
    border-radius: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    background-color: #f3f4f6;
    color: #9ca3af;
    transition: all 0.3s;
}

.circle.active {
    transform: scale(1.25);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    color: white;
}

/* Output Display */
.output-card {
    background-color: var(--card-bg);
    border-radius: 0.5rem;
    border: 1px solid #BEC6D1;
    padding: 1.5rem;
    margin-bottom: 2rem;
}

.output-log {
    background-color: var(--code-bg);
    color: var(--code-text);
    border-radius: 0.5rem;
    padding: 1rem;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.875rem;
    min-height: 3rem;
}

.output-line.new {
    animation: fadeIn 0.3s ease-in;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(5px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Comparison Table */
.comparison-card {
    background-color: var(--card-bg);
    border-radius: 0.5rem;
    border: 1px solid #BEC6D1;
    padding: 1.5rem;
}

.table-wrapper {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
}

th {
    padding: 0.75rem;
    font-weight: 600;
    border-bottom: 2px solid #d1d5db;
}

td {
    padding: 0.75rem;
    border-bottom: 1px solid #e5e7eb;
}

.font-medium {
    font-weight: 500;
}

.hidden {
    display: none;
}
/* Phase 3: four languages side by side */
.phase-card { border: 1px solid #BEC6D1; border-radius: 8px; padding: 12px 16px; margin-bottom: 1rem; }
.phase-bar { display: flex; flex-wrap: wrap; gap: 4px; }
.ph { font-size: 0.8rem; padding: 2px 8px; border-radius: 10px; border: 1px solid #BEC6D1; color: #555555; background: #FFFFFF; white-space: nowrap; }
.ph.done { background: #F4F4F4; color: #8A8A8A; }
.ph.now { background: #BC0031; border-color: #BC0031; color: #FFFFFF; font-weight: 700; }
.narration { margin-top: 8px; font-size: 1.05rem; min-height: 1.5em; }
.code-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin: 1rem 0; }
@media (max-width: 1100px) { .code-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 640px) { .code-grid { grid-template-columns: minmax(0, 1fr); } }
.lang-card { border: 1px solid #BEC6D1; border-radius: 8px; overflow: hidden; display: flex; flex-direction: column; background: #FFFFFF; }
.lang-card.focus { outline: 3px solid #BC0031; outline-offset: 2px; }
.lang-card h2 { color: #FFFFFF; font-size: 1rem; font-weight: 700; padding: 6px 12px; margin: 0; }
.lang-card .code-lines { font-family: "Courier New", Courier, monospace; font-size: 0.8rem; background: #F9F9F9; padding: 10px 12px; overflow-x: auto; flex: 1; }
.lang-card .code-line { white-space: pre; padding: 1px 0; border-left: none; }
.seg { border-radius: 3px; transition: background 0.2s; }
.seg.cmt { color: #8A8A8A; }
.seg.on { background: #F6D2DB; color: #7E0021; font-weight: 700; box-shadow: 0 0 0 2px #F6D2DB; }
.says { font-size: 0.9rem; min-height: 3em; padding: 8px 12px 0; margin: 0; }
.count { font-size: 0.8rem; color: #555555; padding: 4px 12px 10px; margin: 0; }
.count .n { font-family: "Courier New", monospace; font-weight: 700; color: #1F1D21; font-size: 1rem; }
.state-row { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 12px; margin-bottom: 1rem; }
@media (max-width: 640px) { .state-row { grid-template-columns: minmax(0, 1fr); } }
.state-row .hidden { display: block; visibility: hidden; }
.circle.past { background: #D1D5DB; }
.circle.active { background: #BC0031; color: #FFFFFF; }