.tuba-app-container * {
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
}

.tuba-app-container {
    background: #ffffff;
    border-radius: 24px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.08), 0 1px 3px rgba(0,0,0,0.05);
    max-width: 600px;
    margin: 40px auto;
    overflow: hidden;
    position: relative;
    border: 1px solid #f1f5f9;
}

/* Progress Bar */
.tuba-progress-bar {
    width: 100%;
    height: 4px;
    background: #f1f5f9;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 10;
}

.tuba-progress-fill {
    height: 100%;
    width: 33%;
    background: linear-gradient(90deg, #3b82f6, #60a5fa);
    transition: width 0.4s ease;
}

/* Header */
.tuba-app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px 30px;
    border-bottom: 1px solid #f1f5f9;
    background: #ffffff;
}

.tuba-app-header h3 {
    margin: 0;
    font-size: 18px;
    font-weight: 700;
    color: #0f172a;
    text-align: center;
    flex-grow: 1;
}

.tuba-back-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: #64748b;
    padding: 0;
    display: flex;
    transition: color 0.2s;
}

.tuba-back-btn:hover {
    color: #0f172a;
}

/* Steps Wrapper */
.tuba-steps-wrapper {
    position: relative;
    min-height: 400px;
    overflow: hidden;
    background: #fafaf9;
}

.tuba-step {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    padding: 30px;
    opacity: 0;
    transform: translateX(50px);
    pointer-events: none;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    overflow-y: auto;
}

.tuba-step.tuba-step-active {
    opacity: 1;
    transform: translateX(0);
    pointer-events: auto;
    position: relative; /* Allow height to expand */
}

/* Step 1: Topics */
.tuba-topic-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
}

.tuba-topic-card {
    background: #ffffff;
    border: 2px solid #e2e8f0;
    border-radius: 16px;
    padding: 20px;
    display: flex;
    align-items: center;
    cursor: pointer;
    transition: all 0.2s ease;
}

.tuba-topic-card:hover {
    border-color: #3b82f6;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.1);
    transform: translateY(-2px);
}

.tuba-topic-icon {
    font-size: 28px;
    margin-right: 16px;
    background: #f1f5f9;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
}

.tuba-topic-card span {
    font-size: 16px;
    font-weight: 600;
    color: #1e293b;
}

/* Step 2: Calendar */
.tuba-calendar-app {
    background: #fff;
    border-radius: 16px;
    border: 1px solid #e2e8f0;
    padding: 16px;
    margin-bottom: 24px;
}

.tuba-cal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
}

.tuba-cal-header button {
    background: #f1f5f9;
    border: none;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    cursor: pointer;
    font-weight: bold;
    color: #64748b;
}

.tuba-cal-header button:hover {
    background: #e2e8f0;
    color: #0f172a;
}

#tuba-cal-month-year {
    font-weight: 700;
    font-size: 16px;
    color: #0f172a;
}

.tuba-cal-weekdays {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    text-align: center;
    font-size: 12px;
    font-weight: 600;
    color: #94a3b8;
    margin-bottom: 8px;
}

.tuba-cal-days {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 4px;
}

.tuba-day {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 500;
    border-radius: 10px;
    cursor: pointer;
    color: #1e293b;
    transition: all 0.2s;
}

.tuba-day:hover:not(.tuba-day-disabled) {
    background: #eff6ff;
    color: #2563eb;
}

.tuba-day-disabled {
    color: #cbd5e1;
    cursor: not-allowed;
}

.tuba-day-selected {
    background: #2563eb !important;
    color: #fff !important;
    font-weight: 700;
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.3);
}

.tuba-time-selection h4 {
    font-size: 14px;
    color: #64748b;
    margin-top: 0;
    margin-bottom: 12px;
}

.tuba-time-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
}

.tuba-time-slot {
    background: #fff;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    padding: 10px 0;
    text-align: center;
    font-size: 14px;
    font-weight: 600;
    color: #334155;
    cursor: pointer;
    transition: all 0.2s;
}

.tuba-time-slot:hover {
    border-color: #2563eb;
    color: #2563eb;
}

.tuba-time-selected {
    background: #2563eb;
    color: #fff !important;
    border-color: #2563eb;
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.3);
}

/* Step 3: Contact */
.tuba-summary-box {
    background: #eff6ff;
    border-left: 4px solid #3b82f6;
    padding: 12px 16px;
    border-radius: 0 8px 8px 0;
    font-size: 13px;
    color: #1e3a8a;
    margin-bottom: 24px;
    line-height: 1.5;
}

.tuba-form-group {
    margin-bottom: 16px;
}

.tuba-form-group label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: #475569;
    margin-bottom: 6px;
}

.tuba-form-group input {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    font-size: 15px;
    color: #0f172a;
    transition: border-color 0.2s;
    outline: none;
}

.tuba-form-group input:focus {
    border-color: #3b82f6;
}

.tuba-submit-btn {
    width: 100%;
    padding: 16px;
    background: linear-gradient(135deg, #1e40af, #3b82f6);
    color: #fff;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    margin-top: 10px;
    transition: transform 0.2s, box-shadow 0.2s;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.tuba-submit-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(59, 130, 246, 0.4);
}

.tuba-checkbox-label {
    display: flex;
    align-items: flex-start;
    margin: 16px 0;
    cursor: pointer;
    position: relative;
    padding-left: 28px;
}

.tuba-checkbox-label input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
    height: 0;
    width: 0;
}

.tuba-checkmark {
    position: absolute;
    top: 2px;
    left: 0;
    height: 20px;
    width: 20px;
    background-color: #fff;
    border: 2px solid #cbd5e1;
    border-radius: 6px;
    transition: all 0.2s;
}

.tuba-checkbox-label:hover input ~ .tuba-checkmark {
    border-color: #94a3b8;
}

.tuba-checkbox-label input:checked ~ .tuba-checkmark {
    background-color: #3b82f6;
    border-color: #3b82f6;
}

.tuba-checkmark:after {
    content: "";
    position: absolute;
    display: none;
    left: 6px;
    top: 2px;
    width: 4px;
    height: 10px;
    border: solid white;
    border-width: 0 2px 2px 0;
    transform: rotate(45deg);
}

.tuba-checkbox-label input:checked ~ .tuba-checkmark:after {
    display: block;
}

.tuba-checktext {
    font-size: 12px;
    color: #64748b;
    line-height: 1.4;
}

/* Success */
.tuba-success-content {
    text-align: center;
    padding: 20px 0;
}

.tuba-success-icon {
    width: 80px;
    height: 80px;
    background: #dcfce7;
    color: #22c55e;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 24px;
}

.tuba-success-icon svg {
    width: 40px;
    height: 40px;
}

.tuba-success-content h3 {
    margin: 0 0 12px 0;
    font-size: 24px;
    color: #0f172a;
}

.tuba-success-content p {
    color: #475569;
    line-height: 1.6;
}

.tuba-error-msg {
    color: #ef4444;
    text-align: center;
    margin-top: 12px;
    font-size: 14px;
    font-weight: 500;
}

@media (max-width: 600px) {
    .tuba-app-container {
        margin: 0;
        border-radius: 0;
        border-left: none;
        border-right: none;
    }
}